How to get row index number in R?

Question

Suppose I have a list or data frame in R, and I would like to get the row index, how do I do that? That is, I would like to know how many rows a certain matrix consists of.

Answer 1

I'm interpreting your question to be about getting row numbers.

• You can try as.numeric(rownames(df)) if you haven't set the rownames. Otherwise use a sequence of 1:nrow(df).
• The which() function converts a TRUE/FALSE row index into row numbers.