Filtering out multiple columns in R

Question

Supposing a data set with several rows and columns with some columns being 0 (I mean all values in the column are 0\'s). How one can filter out those columns? I have tried w

Answer 1

Just another way using lapply as it is a data.frame. apply internally converts data.frame to a matrix I believe.

df[!unlist(lapply(df, function(x) all(x==0)))]

Or in your case:

df[, 1:99][!unlist(lapply(df[, 1:99], function(x) all(x==0)))]

Edit: Another way using colSums. The trick is to use it after checking for 0.

df[!colSums(df == 0) == nrow(df)]

If you know which columns are numeric (say, 1:99), then replace df with:

df[,1:99][!colSums(df[,1:99] == 0) == nrow(df)]