refer to range of columns by name in R
dataframe, names, r, variables
Solution
A column number can be identified from a column name within a data frame as follows:
which(colnames(mydf)=="a")
where mydf is a data frame and a is the name of the column the column number is required for.
(Source)
This can be used to create a column range:
firstcol = which(colnames(x)=="a")
lastcol = which(colnames(x)=="b")
mydf[c(firstcol:lastcol)]
Problem
I need help with something that might be fairly simple in R. I want to refer to a range of columns in a data frame (e.g., extracting a few select variables). However, I don't know their column numbers. Normally, if I wanted to extract columns 4-10 i would say mydata[,4:10]. However, given that I don't know the column numbers, I would want to refer to them by name. Is there an easy way to do this? in sas or spss it is fairly easy to refer to a range of variables by name. Alternatively, is there an easy way to figure out which column number corresponds to a variable name in R?