terms() and I( ) -- extract variables names only
Hi, I am having difficulties extracting all variables used in a formula. Here's an example of what I am doing:
my.formula <- v1 ~ v2 + v3 + I(v4/v5) out.terms <- terms(my.formula) paste(attr(out.terms, "variables"))[-1]
[1] "v1" "v2" "v3" "I(v4/v5)" BUT what I would like to get is [1] "v1" "v2" "v3" "v4" "v5" Also, if I change I(v4/v5) to I(v4^2) or any other expression, it should only extract the variable (here, V4). Is there a built-in function to do it? Suggestions are extremely appreciated. Thank you for your attention, Alvaro A. Novo R-1.2.0 Linux SuSE 6.4 -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-help-request at stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._