What is the right way to multiply data frame by vector?

Question

I'm trying to multiply a data frame df by a vector v, so that the product is a data frame, where the i-th row is given by df[i,]*v. I can do this, for example, by

df <- data.frame(A=1:5, B=2:6); v <- c(0,2) as.data.frame(t(t(df) * v))    A  B 1  0  4 2  0  6 3  0  8 4  0 10 5  0 12 

I am sure there has to be a more R-style approach (and a very simple one!), but nothing comes on my mind. I even tried something like

apply(df, MARGIN=1, function(x) x*v) 

but still, non-readable constructions like as.data.frame(t(.)) are required.
How can I find an efficient and elegant workaround here?

Answer 1

This works too:

data.frame(mapply(`*`,df,v)) 

In that solution, you are taking advantage of the fact that data.frame is a type of list, so you can iterate over both the elements of df and v at the same time with mapply.

Unfortunately, you are limited in what you can output from mapply: as simple list, or a matrix. If your data are huge, this would likely be more efficient:

data.frame(mapply(`*`,df,v,SIMPLIFY=FALSE)) 

Because it would convert it to a list, which is more efficient to convert to a data.frame.