Question

How to ignore case when using subset function in R?

eos91corr.data <- subset(test.data,select=c(c(X,Y,Z,W,T)))

I would like to select columns with names x,y,z,w,t. what should i do?

Thanks

Answer 1

If you can live without the subset() function, the tolower() function may work:

dat <- data.frame(XY = 1:5, x = 1:5, mm = 1:5,
    y = 1:5, z = 1:5, w = 1:5, t = 1:5, r = 1:5)
dat[,tolower(names(dat)) %in% c("xy","x")]

However, this will return a data.frame with the columns in the order they are in the original dataset dat: both

dat[,tolower(names(dat)) %in% c("xy","x")]

and

dat[,tolower(names(dat)) %in% c("x","xy")]

will yield the same result, although the order of the target names has been reversed.

If you want the columns in the result to be in the order of the target vector, you need to be slightly more fancy. The two following commands both return a data.frame with the columns in the order of the target vector (i.e., the results will be different, with columns switched):

dat[,sapply(c("x","xy"),FUN=function(foo)which(foo==tolower(names(dat))))]
dat[,sapply(c("xy","x"),FUN=function(foo)which(foo==tolower(names(dat))))]