dFr <- data.frame(a=11:14, b=24:21, cc=LETTERS[1:4], dd=rep(c(TRUE,FALSE),2))
extrColsDeX(dFr,c("b","cc","notThere"))
extrColsDeX(dFr,c("b","cc","notThere"), doExtractCols=TRUE)
extrColsDeX(dFr, list(c("nn","b","a"), c("cc","a"),"notThere"))
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