R: Get named variable or evaluate expression from list or...

get.var {mgcv}

R Documentation

Get named variable or evaluate expression from list or data.frame

Description

This routine takes a text string and a data frame or list. It first sees if the string is the name of a variable in the data frame/ list. If it is then the value of this variable is returned. Otherwise the routine tries to evaluate the expression within the data.frame/list (but nowhere else) and if successful returns the result. If neither step works then NULL is returned. The routine is useful for processing gam formulae. If the variable is a matrix then it is coerced to a numeric vector, by default.

Usage

 get.var(txt,data,vecMat=TRUE)

Arguments

`txt`	a text string which is either the name of a variable in `data` or when parsed is an expression that can be evaluated in `data`. It can also be neither in which case the function returns `NULL`.
`data`	A data frame or list.
`vecMat`	Should matrices be coerced to numeric vectors?

Value

The evaluated variable or NULL. May be coerced to a numeric vector if it's a matrix.

Author(s)

Simon N. Wood simon.wood@r-project.org

References

http://www.maths.bris.ac.uk/~sw15190/

Examples

require(mgcv)
y <- 1:4;dat<-data.frame(x=5:10)
get.var("x",dat)
get.var("y",dat)
get.var("x==6",dat)
dat <- list(X=matrix(1:6,3,2))
get.var("X",dat)

[Package mgcv version 1.8-23 Index]