Get named variable or evaluate expression from list or data.frame
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.
get.var(txt,data,vecMat=TRUE)
txt |
a text string which is either the name of a variable in |
data |
A data frame or list. |
vecMat |
Should matrices be coerced to numeric vectors? |
The evaluated variable or NULL
. May be coerced to a numeric vector if it's a matrix.
Simon N. Wood simon.wood@r-project.org
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)
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