Marius Marius - 3 months ago 10
R Question

r - Convert vector of lists with uneven length to a matrix

I have a resulting data frame with only one column that contains lists of uneven lengths:

data = list(
c(349, 364, 393, 356, 357, 394, 334, 394, 343, 365, 349),
c(390, 336, 752, 377),
c(670, 757, 405, 343, 1109, 350, 372),
c(0, 0),
c(),
c(1115, 394, 327, 356, 408, 329, 385, 357, 357))


and i would like to convert it to a matrix, filling the gaps with
NA
.
So it should look something like this:

349, 364, 393, 356, 357, 394, 334, 394, 343, 365, 349
390, 336, 752, 377, NA, NA, NA, NA, NA, NA, NA
670, 757, 405, 343, 1109,350, 372, NA, NA, NA, NA
0, 0, NA, NA, NA, NA, NA, NA, NA, NA, NA
NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA
1115,394, 327, 356, 408, 329, 385, 357, 357, NA, NA


eventually even get rid of the rows with only
NAs

I have tried
data = sapply(data[,1], FUN=unlist)
and then
data = sapply(data, '[', seq(max(sapply(data, length))))
but I keep getting a matrix with all the elements unlisted in one column. Please advise.

Answer

I guess the 'data' should be a list instead of a vector, then the code would work

t(sapply(data, `length<-`, max(lengths(data))))

NOTE: lengths is a faster option (introduced in the recent R versions) that replaces sapply(data, length)

data

data = list(
  c(349, 364, 393, 356, 357, 394, 334, 394, 343, 365, 349),
  c(390, 336, 752, 377),
  c(670, 757, 405, 343, 1109, 350, 372),
  c(0, 0),
  numeric(0),
  c(1115, 394, 327, 356, 408, 329, 385, 357, 357))