# Adjusted predictions and estimated marginal means from regression models

Source:`R/predict_response.R`

`predict_response.Rd`

After fitting a model, it is useful generate model-based estimates (expected
values, or *adjusted predictions*) of the response variable for different
combinations of predictor values. Such estimates can be used to make
inferences about relationships between variables.

The **ggeffects** package computes marginal means and adjusted predicted
values for the response, at the margin of specific values or levels from
certain model terms. The package is built around three core functions:
`predict_response()`

(understanding results), `test_predictions()`

(importance
of results) and `plot()`

(communicate results).

By default, adjusted predictions or marginal means are returned on the
*response* scale, which is the easiest and most intuitive scale to interpret
the results. There are other options for specific models as well, e.g. with
zero-inflation component (see documentation of the `type`

-argument). The
result is returned as structured data frame, which is nicely printed by
default. `plot()`

can be used to easily create figures.

The main function to calculate marginal means and adjusted predictions is
`predict_response()`

, which returns adjusted predictions, marginal means
or averaged counterfactual predictions depending on value of the
`margin`

-argument.

In previous versions of **ggeffects**, the functions `ggpredict()`

, `ggemmeans()`

,
`ggeffect()`

and `ggaverage()`

were used to calculate marginal means and
adjusted predictions. These functions are still available, but `predict_response()`

as a "wrapper" around these functions is the preferred way to calculate marginal
means and adjusted predictions now.

## Usage

```
predict_response(
model,
terms,
margin = "mean_reference",
ci_level = 0.95,
type = "fixed",
condition = NULL,
back_transform = TRUE,
ppd = FALSE,
vcov_fun = NULL,
vcov_type = NULL,
vcov_args = NULL,
weights = NULL,
interval,
verbose = TRUE,
...
)
```

## Arguments

- model
A model object.

- terms
Names of those terms from

`model`

, for which predictions should be displayed (so called*focal terms*). Can be:A character vector, specifying the names of the focal terms. This is the preferred and probably most flexible way to specify focal terms, e.g.

`terms = "x [40:60]"`

, to calculate predictions for the values 40 to 60.A list, where each element is a named vector, specifying the focal terms and their values. This is the "classical" R way to specify focal terms, e.g.

`list(x = 40:60)`

.A formula, e.g.

`terms = ~ x + z`

, which is internally converted to a character vector. This is probably the least flexible way, as you cannot specify representative values for the focal terms.A data frame representing a "data grid" or "reference grid". Predictions are then made for all combinations of the variables in the data frame.

`terms`

at least requires one variable name. The maximum length is four terms, where the second to fourth term indicate the groups, i.e. predictions of the first term are grouped at meaningful values or levels of the remaining terms (see`values_at()`

). It is also possible to define specific values for focal terms, at which adjusted predictions should be calculated (see details below). All remaining covariates that are not specified in`terms`

are "marginalized", see the`margin`

argument in`?predict_response`

. See also argument`condition`

to fix non-focal terms to specific values, and argument`typical`

for`ggpredict()`

or`ggemmeans()`

.- margin
Character string, indicating how to marginalize over the

*non-focal*predictors, i.e. those variables that are*not*specified in`terms`

. Possible values are`"mean_reference"`

,`"mean_mode"`

,`"marginalmeans"`

and`"empirical"`

(or`"counterfactual"`

, aka average "counterfactual" predictions). You can set a default-option for the`margin`

argument via`options()`

, e.g.`options(ggeffects_margin = "empirical")`

, so you don't have to specify your preferred marginalization method each time you call`predict_response()`

. See details in the documentation below.- ci_level
Numeric, the level of the confidence intervals. Use

`ci_level = NA`

if confidence intervals should not be calculated (for instance, due to computation time). Typically, confidence intervals are based on the returned standard errors for the predictions, assuming a t- or normal distribution (based on the model and the available degrees of freedom, i.e. roughly`+/- 1.96 * SE`

). See introduction of this vignette for more details.- type
Character, indicating whether predictions should be conditioned on specific model components or not. Consequently, most options only apply for survival models, mixed effects models and/or models with zero-inflation (and their Bayesian counter-parts); only exception is

`type = "simulate"`

, which is available for some other model classes as well (which respond to`simulate()`

).**Note 1:**For`brmsfit`

-models with zero-inflation component, there is no`type = "zero_inflated"`

nor`type = "zi_random"`

; predicted values for these models*always*condition on the zero-inflation part of the model. The same is true for`MixMod`

-models from**GLMMadaptive**with zero-inflation component (see 'Details').**Note 2:**If`margin = "empirical"`

, or when calling`ggaverage()`

respectively, (i.e. counterfactual predictions), the`type`

argument is handled differently. It is set to`"response"`

by default, but usually accepts all possible options from the`type`

-argument of the model's respective`predict()`

method. E.g., passing a`glm`

object would allow the options`"response"`

,`"link"`

, and`"terms"`

. Thus, the following options apply to`predict_response()`

when`margin`

is*not*`"empirical"`

, and are passed to`ggpredict()`

or`ggemmeans()`

, respectively (depending on the value of`margin`

):`"fixed"`

(or`"fe"`

or`"count"`

)Predicted values are conditioned on the fixed effects or conditional model only (for mixed models: predicted values are on the population-level and

*confidence intervals*are returned, i.e.`re.form = NA`

when calling`predict()`

). For instance, for models fitted with`zeroinfl`

from**pscl**, this would return the predicted mean from the count component (without zero-inflation). For models with zero-inflation component, this type calls`predict(..., type = "link")`

(however, predicted values are back-transformed to the response scale).`"random"`

(or`"re"`

)This only applies to mixed models, and

`type = "random"`

does not condition on the zero-inflation component of the model.`type = "random"`

still returns population-level predictions, however, conditioned on random effects and considering individual level predictions, i.e.`re.form = NULL`

when calling`predict()`

. This may affect the returned predicted values, depending on whether`REML = TRUE`

or`REML = FALSE`

was used for model fitting. Furthermore, unlike`type = "fixed"`

, intervals also consider the uncertainty in the variance parameters (the mean random effect variance, see*Johnson et al. 2014*for details) and hence can be considered as*prediction intervals*. For models with zero-inflation component, this type calls`predict(..., type = "link")`

(however, predicted values are back-transformed to the response scale).To get predicted values for each level of the random effects groups, add the name of the related random effect term to the

`terms`

-argument (for more details, see this vignette).`"zero_inflated"`

(or`"fe.zi"`

or`"zi"`

)Predicted values are conditioned on the fixed effects and the zero-inflation component. For instance, for models fitted with

`zeroinfl`

from**pscl**, this would return the predicted response (`mu*(1-p)`

) and for**glmmTMB**, this would return the expected value`mu*(1-p)`

*without*conditioning on random effects (i.e. random effect variances are not taken into account for the confidence intervals). For models with zero-inflation component, this type calls`predict(..., type = "response")`

. See 'Details'.`"zi_random"`

(or`"re.zi"`

or`"zero_inflated_random"`

)Predicted values are conditioned on the zero-inflation component and take the random effects uncertainty into account. For models fitted with

`glmmTMB()`

,`hurdle()`

or`zeroinfl()`

, this would return the expected value`mu*(1-p)`

. For**glmmTMB**, prediction intervals also consider the uncertainty in the random effects variances. This type calls`predict(..., type = "response")`

. See 'Details'.`"zi_prob"`

(or`"zi.prob"`

)Predicted zero-inflation probability. For

**glmmTMB**models with zero-inflation component, this type calls`predict(..., type = "zlink")`

; models from**pscl**call`predict(..., type = "zero")`

and for**GLMMadaptive**,`predict(..., type = "zero_part")`

is called.`"simulate"`

(or`"sim"`

)Predicted values and confidence resp. prediction intervals are based on simulations, i.e. calls to

`simulate()`

. This type of prediction takes all model uncertainty into account, including random effects variances. Currently supported models are objects of class`lm`

,`glm`

,`glmmTMB`

,`wbm`

,`MixMod`

and`merMod`

. See`...`

for details on number of simulations.`"survival"`

and`"cumulative_hazard"`

(or`"surv"`

and`"cumhaz"`

)Applies only to

`coxph`

-objects from the**survial**-package and calculates the survival probability or the cumulative hazard of an event.

When

`margin = "empirical"`

(or when calling`ggaverage()`

), the`type`

argument accepts all values from the`type`

-argument of the model's respective`predict()`

-method.- condition
Named character vector, which indicates covariates that should be held constant at specific values. Unlike

`typical`

, which applies a function to the covariates to determine the value that is used to hold these covariates constant,`condition`

can be used to define exact values, for instance`condition = c(covariate1 = 20, covariate2 = 5)`

. See 'Examples'.- back_transform
Logical, if

`TRUE`

(the default), predicted values for log- or log-log transformed responses will be back-transformed to original response-scale.- ppd
Logical, if

`TRUE`

, predictions for Stan-models are based on the posterior predictive distribution`rstantools::posterior_predict()`

. If`FALSE`

(the default), predictions are based on posterior draws of the linear predictor`rstantools::posterior_epred()`

. This is roughly comparable to the distinction between*confidence*and*prediction*intervals.`ppd = TRUE`

incorporates the residual variance and hence returned intervals are similar to prediction intervals. Consequently, if`interval = "prediction"`

,`ppd`

is automatically set to`TRUE`

. The`ppd`

argument will be deprecated in a future version. Please use`interval = "prediction"`

instead.- vcov_fun
Variance-covariance matrix used to compute uncertainty estimates (e.g., for confidence intervals based on robust standard errors). This argument accepts a covariance matrix, a function which returns a covariance matrix, or a string which identifies the function to be used to compute the covariance matrix.

A (variance-covariance) matrix

A function which returns a covariance matrix (e.g.,

`stats::vcov()`

)A string which indicates the estimation type for the heteroscedasticity-consistent variance-covariance matrix, e.g.

`vcov_fun = "HC0"`

. Possible values are`"HC0"`

,`"HC1"`

,`"HC2"`

,`"HC3"`

,`"HC4"`

,`"HC4m"`

, and`"HC5"`

, which will then call the`vcovHC()`

-function from the**sandwich**package, using the specified type. Further possible values are`"CR0"`

,`"CR1"`

,`"CR1p"`

,`"CR1S"`

,`"CR2"`

, and`"CR3"`

, which will call the`vcovCR()`

-function from the**clubSandwich**package.A string which indicates the name of the

`vcov*()`

-function from the**sandwich**or**clubSandwich**packages, e.g.`vcov_fun = "vcovCL"`

, which is used to compute (cluster) robust standard errors for predictions.

If

`NULL`

, standard errors (and confidence intervals) for predictions are based on the standard errors as returned by the`predict()`

-function.**Note**that probably not all model objects that work with`ggpredict()`

are also supported by the**sandwich**or**clubSandwich**packages.See details in this vignette.

- vcov_type
Character vector, specifying the estimation type for the robust covariance matrix estimation (see

`?sandwich::vcovHC`

or`?clubSandwich::vcovCR`

for details). Only used when`vcov_fun`

is a character string indicating one of the functions from those packages.- vcov_args
List of named vectors, used as additional arguments that are passed down to

`vcov_fun`

.- weights
Character vector, naming the weigthing variable in the data, or a vector of weights (of same length as the number of observations in the data). Only applies to

`margin = "empirical"`

.- interval
Type of interval calculation, can either be

`"confidence"`

(default) or`"prediction"`

. May be abbreviated. Unlike*confidence intervals*,*prediction intervals*include the residual variance (sigma^2) to account for the uncertainty of predicted values. For mixed models,`interval = "prediction"`

is the default for`type = "random"`

. When`type = "fixed"`

, the default is`interval = "confidence"`

. Note that prediction intervals are not available for all models, but only for models that work with`insight::get_sigma()`

. For Bayesian models, when`interval = "confidence"`

, predictions are based on posterior draws of the linear predictor`rstantools::posterior_epred()`

. If`interval = "prediction"`

,`rstantools::posterior_predict()`

is called.- verbose
Toggle messages or warnings.

- ...
If

`margin`

is set to`"mean_reference"`

or`"mean_mode"`

, arguments are passed down to`ggpredict()`

(further down to`predict()`

); for`margin = "marginalmeans"`

, further arguments passed down to`ggemmeans()`

and thereby to`emmeans::emmeans()`

; if`margin = "empirical"`

, further arguments are passed down to`marginaleffects::avg_predictions()`

. If`type = "simulate"`

,`...`

may also be used to set the number of simulation, e.g.`nsim = 500`

. When calling`ggeffect()`

, further arguments passed down to`effects::Effect()`

.

## Value

A data frame (with `ggeffects`

class attribute) with consistent data columns:

`"x"`

: the values of the first term in`terms`

, used as x-position in plots.`"predicted"`

: the predicted values of the response, used as y-position in plots.`"std.error"`

: the standard error of the predictions.*Note that the standard errors are always on the link-scale, and not back-transformed for non-Gaussian models!*`"conf.low"`

: the lower bound of the confidence interval for the predicted values.`"conf.high"`

: the upper bound of the confidence interval for the predicted values.`"group"`

: the grouping level from the second term in`terms`

, used as grouping-aesthetics in plots.`"facet"`

: the grouping level from the third term in`terms`

, used to indicate facets in plots.The estimated marginal means (or predicted values) are always on the response scale!

For proportional odds logistic regression (see

`?MASS::polr`

) resp. cumulative link models (e.g., see`?ordinal::clm`

), an additional column`"response.level"`

is returned, which indicates the grouping of predictions based on the level of the model's response.Note that for convenience reasons, the columns for the intervals are always named

`"conf.low"`

and`"conf.high"`

, even though for Bayesian models credible or highest posterior density intervals are returned.There is an

`as.data.frame()`

method for objects of class`ggeffects`

, which has an`terms_to_colnames`

argument, to use the term names as column names instead of the standardized names`"x"`

etc.

## Note

**Printing Results**

The `print()`

method gives a clean output (especially for predictions by
groups), and indicates at which values covariates were held constant.
Furthermore, the `print()`

method has several arguments to customize the
output. See this vignette
for details.

**Limitations**

The support for some models, for example from package **MCMCglmm**, is not
fully tested and may fail for certain models. If you encounter any errors,
please file an issue at Github.

## Supported Models

A list of supported models can be found at the package website.
Support for models varies by marginalization method (the `margin`

argument),
i.e. although `predict_response()`

supports most models, some models are only
supported exclusively by one of the four downstream functions (`ggpredict()`

,
`ggemmeans()`

, `ggeffect()`

or `ggaverage()`

). This means that not all models
work for every `margin`

option of `predict_response()`

.

## Holding covariates at constant values, or how to marginalize over the *non-focal* predictors

`predict_response()`

is a wrapper around `ggpredict()`

, `ggemmeans()`

and
`ggaverage()`

. Depending on the value of the `margin`

argument,
`predict_response()`

calls one of those functions. The `margin`

argument
indicates how to marginalize over the *non-focal* predictors, i.e. those
variables that are *not* specified in `terms`

. Possible values are:

`"mean_reference"`

and`"mean_mode"`

: For`"mean_reference"`

, non-focal predictors are set to their mean (numeric variables), reference level (factors), or "most common" value (mode) in case of character vectors. For`"mean_mode"`

, non-focal predictors are set to their mean (numeric variables) or mode (factors, or "most common" value in case of character vectors).These predictons represent a rather "theoretical" view on your data, which does not necessarily exactly reflect the characteristics of your sample. It helps answer the question, "What is the predicted value of the response at meaningful values or levels of my focal terms for a 'typical' observation in my data?", where 'typical' refers to certain characteristics of the remaining predictors.

`"marginalmeans"`

: non-focal predictors are set to their mean (numeric variables) or averaged over the levels or "values" for factors and character vectors. Averaging over the factor levels of non-focal terms computes a kind of "weighted average" for the values at which these terms are hold constant. Thus, non-focal categorical terms are conditioned on "weighted averages" of their levels.These predictions come closer to the sample, because all possible values and levels of the non-focal predictors are taken into account. It would answer the question, "What is the predicted value of the response at meaningful values or levels of my focal terms for an 'average' observation in my data?". It refers to randomly picking a subject of your sample and the result you get on average.

`"empirical"`

(or`"counterfactual"`

): non-focal predictors are averaged over the observations in the sample. The response is predicted for each subject in the data and predicted values are then averaged across all subjects, aggregated/grouped by the focal terms. In particular, averaging is applied to*counterfactual predictions*(Dickerman and Hernan 2020). There is a more detailed description in this vignette.Counterfactual predictions are useful, insofar as the results can also be transferred to other contexts. It answers the question, "What is the predicted value of the response at meaningful values or levels of my focal terms for the 'average' observation in the population?". It does not only refer to the actual data in your sample, but also "what would be if" we had more data, or if we had data from a different population. This is where "counterfactual" refers to.

You can set a default-option for the `margin`

argument via `options()`

, e.g.
`options(ggeffects_margin = "empirical")`

, so you don't have to specify your
"default" marginalization method each time you call `predict_response()`

.
Use `options(ggeffects_margin = NULL)`

to remove that setting.

The `condition`

argument can be used to fix non-focal terms to specific
values.

## Marginal Means and Adjusted Predictions at Specific Values

Meaningful values of focal terms can be specified via the `terms`

argument.
Specifying meaningful or representative values as string pattern is the
preferred way in the **ggeffects** package. However, it is also possible to
use a `list()`

for the focal terms if prefer the "classical" R way. `terms`

can also be a data (or reference) grid provided as data frame. All options
are described in this vignette.

Indicating levels in square brackets allows for selecting only certain
groups or values resp. value ranges. The term name and the start of the
levels in brackets must be separated by a whitespace character, e.g.
`terms = c("age", "education [1,3]")`

. Numeric ranges, separated with colon,
are also allowed: `terms = c("education", "age [30:60]")`

. The stepsize for
ranges can be adjusted using `by`

, e.g. `terms = "age [30:60 by=5]"`

.

The `terms`

argument also supports the same shortcuts as the `values`

argument
in `values_at()`

. So `terms = "age [meansd]"`

would return predictions for
the values one standard deviation below the mean age, the mean age and one SD
above the mean age. `terms = "age [quart2]"`

would calculate predictions at
the value of the lower, median and upper quartile of age.

Furthermore, it is possible to specify a function name. Values for predictions
will then be transformed, e.g. `terms = "income [exp]"`

. This is useful when
model predictors were transformed for fitting the model and should be
back-transformed to the original scale for predictions. It is also possible
to define own functions (see
this vignette).

Instead of a function, it is also possible to define the name of a variable
with specific values, e.g. to define a vector `v = c(1000, 2000, 3000)`

and
then use `terms = "income [v]"`

.

You can take a random sample of any size with `sample=n`

, e.g
`terms = "income [sample=8]"`

, which will sample eight values from
all possible values of the variable `income`

. This option is especially
useful for plotting predictions at certain levels of random effects
group levels, where the group factor has too many levels to be completely
plotted. For more details, see
this vignette.

Finally, numeric vectors for which no specific values are given, a "pretty range"
is calculated (see `pretty_range()`

), to avoid memory allocation problems
for vectors with many unique values. If a numeric vector is specified as
second or third term (i.e. if this focal term is used for "stratification"),
representative values (see `values_at()`

) are chosen (unless other values
are specified), which are typically the mean value, as well as one standard
deviation below and above the mean. If all values for a numeric vector should
be used to compute predictions, you may use e.g. `terms = "age [all]"`

. See
also package vignettes.

To create a pretty range that should be smaller or larger than the default
range (i.e. if no specific values would be given), use the `n`

tag, e.g.
`terms="age [n=5]"`

or `terms="age [n=12]"`

. Larger values for `n`

return a
larger range of predicted values.

## Bayesian Regression Models

`predict_response()`

also works with **Stan**-models from the **rstanarm** or
**brms**-packages. The predicted values are the median value of all drawn
posterior samples. Standard errors are the median absolute deviation of the
posterior samples. The confidence intervals for Stan-models are Bayesian
predictive intervals. By default, the predictions are based on
`rstantools::posterior_epred()`

and hence have the limitations that the
uncertainty of the error term (residual variance) is not taken into account.
The recommendation is to use the posterior predictive distribution
(`rstantools::posterior_predict()`

), i.e. setting `interval = "prediction"`

.

## Zero-Inflated and Zero-Inflated Mixed Models with brms

Models of class `brmsfit`

always condition on the zero-inflation component,
if the model has such a component. Hence, there is no `type = "zero_inflated"`

nor `type = "zi_random"`

for `brmsfit`

-models, because predictions are based
on draws of the posterior distribution, which already account for the
zero-inflation part of the model.

**Zero-Inflated and Zero-Inflated Mixed Models with glmmTMB**

If `model`

is of class `glmmTMB`

, `hurdle`

, `zeroinfl`

or `zerotrunc`

, and
`margin`

is *not* set to `"empirical`

, simulations from a multivariate
normal distribution (see `?MASS::mvrnorm`

) are drawn to calculate `mu*(1-p)`

.
Confidence intervals are then based on quantiles of these results.
For `type = "zi_random"`

, prediction intervals also take the uncertainty in
the random-effect paramters into account (see also *Brooks et al. 2017*,
pp.391-392 for details).

An alternative for models fitted with **glmmTMB** that take all model
uncertainties into account are simulations based on `simulate()`

, which
is used when `type = "simulate"`

(see *Brooks et al. 2017*, pp.392-393 for
details).

Finally, if `margin = "empirical"`

, the returned predictions are already
conditioned on the zero-inflation part (and possible random effects) of the
model, thus these are most comparable to the `type = "simulate"`

option. In
other words, if all model components should be taken into account for
predictions, you should consider using `margin = "empirical"`

.

## MixMod-models from GLMMadaptive

Predicted values for the fixed effects component (`type = "fixed"`

or
`type = "zero_inflated"`

) are based on `predict(..., type = "mean_subject")`

,
while predicted values for random effects components (`type = "random"`

or
`type = "zi_random"`

) are calculated with `predict(..., type = "subject_specific")`

(see `?GLMMadaptive::predict.MixMod`

for details). The latter option
requires the response variable to be defined in the `newdata`

-argument
of `predict()`

, which will be set to its typical value (see
`values_at()`

).

## Multinomial Models

`polr`

, `clm`

models, or more generally speaking, models with ordinal or
multinominal outcomes, have an additional column `response.level`

, which
indicates with which level of the response variable the predicted values are
associated.

## References

Brooks ME, Kristensen K, Benthem KJ van, Magnusson A, Berg CW, Nielsen A, et al. glmmTMB Balances Speed and Flexibility Among Packages for Zero-inflated Generalized Linear Mixed Modeling. The R Journal. 2017;9: 378-400.

Johnson PC. 2014. Extension of Nakagawa & Schielzeth's R2GLMM to random slopes models. Methods Ecol Evol, 5: 944-946.

Dickerman BA, Hernan, MA. Counterfactual prediction is not only for causal inference. Eur J Epidemiol 35, 615–617 (2020).

## Examples

```
library(sjlabelled)
data(efc)
fit <- lm(barthtot ~ c12hour + neg_c_7 + c161sex + c172code, data = efc)
predict_response(fit, terms = "c12hour")
#> # Predicted values of Total score BARTHEL INDEX
#>
#> c12hour | Predicted | 95% CI
#> ----------------------------------
#> 0 | 75.44 | 73.25, 77.63
#> 20 | 70.38 | 68.56, 72.19
#> 45 | 64.05 | 62.39, 65.70
#> 65 | 58.98 | 57.15, 60.80
#> 85 | 53.91 | 51.71, 56.12
#> 105 | 48.85 | 46.14, 51.55
#> 125 | 43.78 | 40.51, 47.05
#> 170 | 32.38 | 27.73, 37.04
#>
#> Adjusted for:
#> * neg_c_7 = 11.84
#> * c161sex = 1.76
#> * c172code = 1.97
#>
#> Not all rows are shown in the output. Use `print(..., n = Inf)` to show
#> all rows.
predict_response(fit, terms = c("c12hour", "c172code"))
#> # Predicted values of Total score BARTHEL INDEX
#>
#> c172code: low level of education
#>
#> c12hour | Predicted | 95% CI
#> ----------------------------------
#> 0 | 74.75 | 71.26, 78.23
#> 30 | 67.15 | 64.03, 70.26
#> 55 | 60.81 | 57.77, 63.86
#> 85 | 53.22 | 49.95, 56.48
#> 115 | 45.62 | 41.86, 49.37
#> 170 | 31.69 | 26.59, 36.78
#>
#> c172code: intermediate level of education
#>
#> c12hour | Predicted | 95% CI
#> ----------------------------------
#> 0 | 75.46 | 73.28, 77.65
#> 30 | 67.87 | 66.16, 69.57
#> 55 | 61.53 | 59.82, 63.25
#> 85 | 53.93 | 51.72, 56.14
#> 115 | 46.34 | 43.35, 49.32
#> 170 | 32.40 | 27.74, 37.07
#>
#> c172code: high level of education
#>
#> c12hour | Predicted | 95% CI
#> ----------------------------------
#> 0 | 76.18 | 72.81, 79.55
#> 30 | 68.58 | 65.41, 71.76
#> 55 | 62.25 | 59.00, 65.50
#> 85 | 54.65 | 51.03, 58.27
#> 115 | 47.05 | 42.85, 51.26
#> 170 | 33.12 | 27.50, 38.74
#>
#> Adjusted for:
#> * neg_c_7 = 11.84
#> * c161sex = 1.76
#>
#> Not all rows are shown in the output. Use `print(..., n = Inf)` to show
#> all rows.
# more compact table layout for printing
out <- predict_response(fit, terms = c("c12hour", "c172code", "c161sex"))
print(out, collapse_table = TRUE)
#> # Predicted values of Total score BARTHEL INDEX
#>
#> c12hour | c172code | c161sex | Predicted | 95% CI
#> ---------------------------------------------------------------------------------
#> 0 | low level of education | [1] Male | 73.95 | 69.35, 78.56
#> 45 | | | 62.56 | 58.22, 66.89
#> 85 | | | 52.42 | 47.89, 56.96
#> 170 | | | 30.89 | 24.84, 36.95
#> 0 | | [2] Female | 75.00 | 71.40, 78.59
#> 45 | | | 63.60 | 60.45, 66.74
#> 85 | | | 53.46 | 50.12, 56.80
#> 170 | | | 31.93 | 26.82, 37.05
#> 0 | intermediate level of education | [1] Male | 74.67 | 71.05, 78.29
#> 45 | | | 63.27 | 59.88, 66.67
#> 85 | | | 53.14 | 49.39, 56.89
#> 170 | | | 31.61 | 25.97, 37.25
#> 0 | | [2] Female | 75.71 | 73.31, 78.12
#> 45 | | | 64.32 | 62.41, 66.22
#> 85 | | | 54.18 | 51.81, 56.56
#> 170 | | | 32.65 | 27.94, 37.37
#> 0 | high level of education | [1] Male | 75.39 | 71.03, 79.75
#> 45 | | | 63.99 | 59.72, 68.26
#> 85 | | | 53.86 | 49.22, 58.50
#> 170 | | | 32.33 | 25.94, 38.72
#> 0 | | [2] Female | 76.43 | 72.88, 79.98
#> 45 | | | 65.03 | 61.67, 68.39
#> 85 | | | 54.90 | 51.15, 58.65
#> 170 | | | 33.37 | 27.69, 39.05
#>
#> Adjusted for:
#> * neg_c_7 = 11.84
#>
#> Not all rows are shown in the output. Use `print(..., n = Inf)` to show
#> all rows.
# specified as formula
predict_response(fit, terms = ~ c12hour + c172code + c161sex)
#> # Predicted values of Total score BARTHEL INDEX
#>
#> c172code: low level of education
#> c161sex: [1] Male
#>
#> c12hour | Predicted | 95% CI
#> ----------------------------------
#> 0 | 73.95 | 69.35, 78.56
#> 45 | 62.56 | 58.22, 66.89
#> 85 | 52.42 | 47.89, 56.96
#> 170 | 30.89 | 24.84, 36.95
#>
#> c172code: low level of education
#> c161sex: [2] Female
#>
#> c12hour | Predicted | 95% CI
#> ----------------------------------
#> 0 | 75.00 | 71.40, 78.59
#> 45 | 63.60 | 60.45, 66.74
#> 85 | 53.46 | 50.12, 56.80
#> 170 | 31.93 | 26.82, 37.05
#>
#> c172code: intermediate level of education
#> c161sex: [1] Male
#>
#> c12hour | Predicted | 95% CI
#> ----------------------------------
#> 0 | 74.67 | 71.05, 78.29
#> 45 | 63.27 | 59.88, 66.67
#> 85 | 53.14 | 49.39, 56.89
#> 170 | 31.61 | 25.97, 37.25
#>
#> c172code: intermediate level of education
#> c161sex: [2] Female
#>
#> c12hour | Predicted | 95% CI
#> ----------------------------------
#> 0 | 75.71 | 73.31, 78.12
#> 45 | 64.32 | 62.41, 66.22
#> 85 | 54.18 | 51.81, 56.56
#> 170 | 32.65 | 27.94, 37.37
#>
#> c172code: high level of education
#> c161sex: [1] Male
#>
#> c12hour | Predicted | 95% CI
#> ----------------------------------
#> 0 | 75.39 | 71.03, 79.75
#> 45 | 63.99 | 59.72, 68.26
#> 85 | 53.86 | 49.22, 58.50
#> 170 | 32.33 | 25.94, 38.72
#>
#> c172code: high level of education
#> c161sex: [2] Female
#>
#> c12hour | Predicted | 95% CI
#> ----------------------------------
#> 0 | 76.43 | 72.88, 79.98
#> 45 | 65.03 | 61.67, 68.39
#> 85 | 54.90 | 51.15, 58.65
#> 170 | 33.37 | 27.69, 39.05
#>
#> Adjusted for:
#> * neg_c_7 = 11.84
#>
#> Not all rows are shown in the output. Use `print(..., n = Inf)` to show
#> all rows.
# only range of 40 to 60 for variable 'c12hour'
predict_response(fit, terms = "c12hour [40:60]")
#> # Predicted values of Total score BARTHEL INDEX
#>
#> c12hour | Predicted | 95% CI
#> ----------------------------------
#> 40 | 65.31 | 63.66, 66.96
#> 43 | 64.55 | 62.90, 66.20
#> 45 | 64.05 | 62.39, 65.70
#> 47 | 63.54 | 61.88, 65.20
#> 50 | 62.78 | 61.11, 64.45
#> 53 | 62.02 | 60.33, 63.71
#> 55 | 61.51 | 59.80, 63.22
#> 60 | 60.25 | 58.49, 62.01
#>
#> Adjusted for:
#> * neg_c_7 = 11.84
#> * c161sex = 1.76
#> * c172code = 1.97
#>
#> Not all rows are shown in the output. Use `print(..., n = Inf)` to show
#> all rows.
# terms as named list
predict_response(fit, terms = list(c12hour = 40:60))
#> # Predicted values of Total score BARTHEL INDEX
#>
#> c12hour | Predicted | 95% CI
#> ----------------------------------
#> 40 | 65.31 | 63.66, 66.96
#> 43 | 64.55 | 62.90, 66.20
#> 45 | 64.05 | 62.39, 65.70
#> 47 | 63.54 | 61.88, 65.20
#> 50 | 62.78 | 61.11, 64.45
#> 53 | 62.02 | 60.33, 63.71
#> 55 | 61.51 | 59.80, 63.22
#> 60 | 60.25 | 58.49, 62.01
#>
#> Adjusted for:
#> * neg_c_7 = 11.84
#> * c161sex = 1.76
#> * c172code = 1.97
#>
#> Not all rows are shown in the output. Use `print(..., n = Inf)` to show
#> all rows.
# covariate "neg_c_7" is held constant at a value of 11.84 (its mean value).
# To use a different value, use "condition"
predict_response(fit, terms = "c12hour [40:60]", condition = c(neg_c_7 = 20))
#> # Predicted values of Total score BARTHEL INDEX
#>
#> c12hour | Predicted | 95% CI
#> ----------------------------------
#> 40 | 46.56 | 42.58, 50.55
#> 43 | 45.80 | 41.84, 49.76
#> 45 | 45.30 | 41.35, 49.24
#> 47 | 44.79 | 40.86, 48.72
#> 50 | 44.03 | 40.11, 47.94
#> 53 | 43.27 | 39.37, 47.17
#> 55 | 42.76 | 38.87, 46.65
#> 60 | 41.50 | 37.62, 45.37
#>
#> Adjusted for:
#> * c161sex = 1.76
#> * c172code = 1.97
#>
#> Not all rows are shown in the output. Use `print(..., n = Inf)` to show
#> all rows.
# to plot ggeffects-objects, you can use the 'plot()'-function.
# the following examples show how to build your ggplot by hand.
# \donttest{
# plot predicted values, remaining covariates held constant
library(ggplot2)
mydf <- predict_response(fit, terms = "c12hour")
ggplot(mydf, aes(x, predicted)) +
geom_line() +
geom_ribbon(aes(ymin = conf.low, ymax = conf.high), alpha = 0.1)
# three variables, so we can use facets and groups
mydf <- predict_response(fit, terms = c("c12hour", "c161sex", "c172code"))
ggplot(mydf, aes(x = x, y = predicted, colour = group)) +
stat_smooth(method = "lm", se = FALSE) +
facet_wrap(~facet, ncol = 2)
#> `geom_smooth()` using formula = 'y ~ x'
# select specific levels for grouping terms
mydf <- predict_response(fit, terms = c("c12hour", "c172code [1,3]", "c161sex"))
ggplot(mydf, aes(x = x, y = predicted, colour = group)) +
stat_smooth(method = "lm", se = FALSE) +
facet_wrap(~facet) +
labs(
y = get_y_title(mydf),
x = get_x_title(mydf),
colour = get_legend_title(mydf)
)
#> `geom_smooth()` using formula = 'y ~ x'
# level indication also works for factors with non-numeric levels
# and in combination with numeric levels for other variables
data(efc)
efc$c172code <- sjlabelled::as_label(efc$c172code)
fit <- lm(barthtot ~ c12hour + neg_c_7 + c161sex + c172code, data = efc)
predict_response(fit, terms = c("c12hour",
"c172code [low level of education, high level of education]",
"c161sex [1]"))
#> # Predicted values of Total score BARTHEL INDEX
#>
#> c172code: low level of education
#>
#> c12hour | Predicted | 95% CI
#> ----------------------------------
#> 0 | 72.81 | 67.90, 77.72
#> 30 | 65.22 | 60.53, 69.90
#> 55 | 58.89 | 54.22, 63.55
#> 85 | 51.29 | 46.45, 56.13
#> 115 | 43.69 | 38.48, 48.90
#> 170 | 29.76 | 23.48, 36.05
#>
#> c172code: high level of education
#>
#> c12hour | Predicted | 95% CI
#> ----------------------------------
#> 0 | 74.03 | 69.23, 78.83
#> 30 | 66.43 | 61.74, 71.13
#> 55 | 60.10 | 55.33, 64.88
#> 85 | 52.51 | 47.45, 57.56
#> 115 | 44.91 | 39.39, 50.43
#> 170 | 30.98 | 24.28, 37.68
#>
#> Adjusted for:
#> * neg_c_7 = 11.84
#>
#> Not all rows are shown in the output. Use `print(..., n = Inf)` to show
#> all rows.
# when "terms" is a named list
predict_response(fit, terms = list(
c12hour = seq(0, 170, 30),
c172code = c("low level of education", "high level of education"),
c161sex = 1)
)
#> # Predicted values of Total score BARTHEL INDEX
#>
#> c172code: low level of education
#>
#> c12hour | Predicted | 95% CI
#> ----------------------------------
#> 0 | 72.81 | 67.90, 77.72
#> 30 | 65.22 | 60.53, 69.90
#> 60 | 57.62 | 52.94, 62.29
#> 90 | 50.02 | 45.14, 54.91
#> 120 | 42.43 | 37.14, 47.72
#> 150 | 34.83 | 28.98, 40.67
#>
#> c172code: high level of education
#>
#> c12hour | Predicted | 95% CI
#> ----------------------------------
#> 0 | 74.03 | 69.23, 78.83
#> 30 | 66.43 | 61.74, 71.13
#> 60 | 58.84 | 54.03, 63.64
#> 90 | 51.24 | 46.11, 56.36
#> 120 | 43.64 | 38.03, 49.26
#> 150 | 36.05 | 29.82, 42.28
#>
#> Adjusted for:
#> * neg_c_7 = 11.84
# use categorical value on x-axis, use axis-labels, add error bars
dat <- predict_response(fit, terms = c("c172code", "c161sex"))
ggplot(dat, aes(x, predicted, colour = group)) +
geom_point(position = position_dodge(0.1)) +
geom_errorbar(
aes(ymin = conf.low, ymax = conf.high),
position = position_dodge(0.1)
) +
scale_x_discrete(breaks = 1:3, labels = get_x_labels(dat))
# 3-way-interaction with 2 continuous variables
data(efc)
# make categorical
efc$c161sex <- as_factor(efc$c161sex)
fit <- lm(neg_c_7 ~ c12hour * barthtot * c161sex, data = efc)
# select only levels 30, 50 and 70 from continuous variable Barthel-Index
dat <- predict_response(fit, terms = c("c12hour", "barthtot [30,50,70]", "c161sex"))
ggplot(dat, aes(x = x, y = predicted, colour = group)) +
stat_smooth(method = "lm", se = FALSE, fullrange = TRUE) +
facet_wrap(~facet) +
labs(
colour = get_legend_title(dat),
x = get_x_title(dat),
y = get_y_title(dat),
title = get_title(dat)
)
#> `geom_smooth()` using formula = 'y ~ x'
# or with ggeffects' plot-method
plot(dat, show_ci = FALSE)
# }
# predictions for polynomial terms
data(efc)
fit <- glm(
tot_sc_e ~ c12hour + e42dep + e17age + I(e17age^2) + I(e17age^3),
data = efc,
family = poisson()
)
predict_response(fit, terms = "e17age")
#> # Predicted counts of Services for elderly
#>
#> e17age | Predicted | 95% CI
#> -------------------------------
#> 65 | 1.25 | 1.00, 1.55
#> 69 | 0.97 | 0.87, 1.09
#> 74 | 0.90 | 0.80, 1.01
#> 78 | 0.94 | 0.85, 1.04
#> 82 | 1.01 | 0.92, 1.11
#> 87 | 1.06 | 0.94, 1.18
#> 91 | 0.97 | 0.84, 1.12
#> 103 | 0.22 | 0.07, 0.72
#>
#> Adjusted for:
#> * c12hour = 42.29
#> * e42dep = 2.94
#>
#> Not all rows are shown in the output. Use `print(..., n = Inf)` to show
#> all rows.
```