Compute the coefficient of variation.

## Arguments

x |
Fitted linear model of class `lm` , `merMod` (lme4)
or `lme` (nlme). |

... |
More fitted model objects, to compute multiple coefficients of
variation at once. |

## Value

Numeric, the coefficient of variation.

## Details

The advantage of the cv is that it is unitless. This allows
coefficient of variation to be compared to each other in ways
that other measures, like standard deviations or root mean
squared residuals, cannot be.

## Examples

```
data(efc)
fit <- lm(barthtot ~ c160age + c12hour, data = efc)
cv(fit)
#> [1] 0.3948098
```