short formula call for many variables when buildin

Question

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• Formula with dynamic number of variables 5 answers

I am trying to build a regression model with lm(...). My dataset has lots of features(>50). I do not want to write my code as lm(output~feature1+feature2+feature3+...+feature70). I was wondering what is the short hand notation to write this code.

Answer 1

Could also try things like:

lm(output ~ myData[,2:71], data=myData)

Assuming output is the first column feature1:feature70 are the next 70 columns.

Or

features <- paste("feature",1:70, sep="")
lm(output ~ myData[,features], data=myData)

Is probably smarter as it doesn't matter where in amongst your data the columns are.

Might cause issues if there's row's removed for NA's though...

Answer 2

You can use . as described in the help page for formula. The . stands for "all columns not otherwise in the formula".

lm(output ~ ., data = myData).

Alternatively, construct the formula manually with paste. This example is from the as.formula() help page:

xnam <- paste("x", 1:25, sep="")
(fmla <- as.formula(paste("y ~ ", paste(xnam, collapse= "+"))))

You can then insert this object into regression function: lm(fmla, data = myData).