mgcv (version 1.3-31)

get.var: 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.

Usage

get.var(txt,data)

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.

Value

• The evaluated variable, or NULL

References

http://www.maths.bath.ac.uk/~sw283/

See Also

gam

Examples

y <- 1:4;dat<-data.frame(x=5:10)
get.var("x",dat)
get.var("y",dat)
get.var("x==6",dat)