Subset from a list of data.frames

Question

I have a list of data.frames. Suppose the list is composed by 10 data.frames. I would like first of all rename each list of data.frames according to a list of names stored in another file. Second, suppose the data.frames is named "Pippo" and "Pippo" is an element of the data.frame. I would like to subset in the following way:

Suppose this is the data.frame named "Pippo" from the list of data.frames:

 Name Sample1 Sample2 Sample3 Sample4 John 1 0 -3 -7 Michael 0 4 2 21 Pippo 1 1 23 0 

I would like to subset all the elements according to "Pippo" value == 1 so that the output will be:

 Name Sample1 Sample2 John 1 0 Michael 0 4 Pippo 1 1 

This will be done for all the names of the list of data.frames since each name is an element of the data.frame.

Answer 1

Let ldf be your list of dataframes. You can change the list's names using:

names(ldf) <- v

where v is a character vector.

For the second step (subsetting), this should work:

subset.ldf <- mapply(ldf, names(ldf),
                     function(x, name) x[, x[name, ] == 1, drop = FALSE])

Answer 2

Or a vector based solution:

d = data.frame(name=c('john','michael','pippo'), sample1 = c(1,0,1),
           sample2 = c(0,4,1), sample3 = c(-3,2,23), sample4 = c(-7,21,0))

sel = d[d$name == 'pippo',2:5]; sel = c(TRUE, sel == 1)
d[,sel]