# Model functions

## inv() function

inv(`v`[`r`])

forms the reciprocal of `v + r`.
This may also be used to transform the response variable.
## log() function

log(`v`[`r`]

forms the natural log of `v + r`.
This may also be used to transform the response variable.
## pow() function

pow(`v`,`p`[,`r`]

raises `v + r`.to power ` p`.
This may also be used to transform the response variable.
This is equivalent to natural log transformation if
` p` is zero.
## sqrt() function

sqrt(`v`[`r`])

forms the square root of `v + r`.
This may also be used to transform the response variable.
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