How to delete empty data.frame in a list after subsetting in R

Question

Suppose I'm subsetting from a list of named data.frames with respect to a subsetting variable called long.

After subsetting, some data.frames in the list may be empty because there is no match for subsetting in them.

I was wondering how I could delete all such empty data.frames in my final output.

A simple example, and my unsuccessful solution are shown below:

b <- list(Study1 = data.frame(d = 6:8, long = c(F, F,F)), Study2 = data.frame(d = 9:11, long = c(T, T, F)) )


( h <- lapply(b, subset, subset = long) ) ## subset with respect to "long"

## OUTPUT:

   $Study1
   [1] d    long
    <0 rows> (or 0-length row.names)   ## This data.frame is empty!! must be deleted ##!

   $Study2
    d long
    1  9 TRUE
    2 10 TRUE


## I tried the following with no success: ##

for(i in 1:2) if(nrow(h[[i]]) == 0) h[[i]] <- NULL else h[[i]]

Answer 1

Simply Filter by number of rows:

new_list_of_dfs <- Filter(NROW, list_of_dfs)