I have a data frame (df) with colums x, y and z. e.g. df <- data.frame(x = sample(4), y = sample(4), z = sample(4)) I can extract column z by: df$z or df[3] I can also extract columns x,y by: df[1:2] or by df[-3].
Is it possible to extract x,y columns in a "symbolic" fashion i.e. by equivalent of df[-z] (which is illegal) ???
Or alternativeley, is there an equivalent of "index" function, which would return index of the column given name ?
colindex=function(dataframe,columname){ return(which(dimnames(dataframe)[[2]]==columname)) }
> x=data.frame(diag(3)) > colindex(x,"X2") [1] 2
Eric
colindex(x,"X2")
-------------------------------------------------- L'erreur est certes humaine, mais un vrai d�sastre n�cessite un ou deux ordinateurs. Citation anonyme -------------------------------------------------- Eric Lecoutre Informaticien/Statisticien Institut de Statistique / UCL
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