CODEWITHSUNDEEP
rclassmatrix
user4080360
user4080360

Reputation:

vapply and matrix; problem returning class

Is there any workaround solution for the following problem?

> bb = list(x=matrix(0,0,0))
> bb = list(x=matrix(0,0,0), y=numeric(0))
> vapply(bb, class, character(1))
Error in vapply(bb, class, character(1)) : values must be length 1,
 but FUN(X[[1]]) result is length 2

Upvotes: 1

Views: 131

Answers (1)

akrun
akrun

Reputation: 886968

The first list element returns two values for class - matrix and array. So we may need to subset by indexing with [1] (using a lambda/anonymous function) as we specify that the length is 1 and the return value type as character with character(1)

vapply(bb, function(x) class(x)[1], character(1))
#      x         y 
# "matrix" "numeric"

If we need both values, one option is paste them together

vapply(bb, function(x) toString(class(x)), character(1))
#             x               y 
#"matrix, array"       "numeric"

Or append NA at the end and extract the first two elements, while specifying the character(2)

vapply(bb, function(x) c(class(x), NA_character_)[1:2], character(2))
#.      x        y        
#[1,] "matrix" "numeric"
#[2,] "array"  NA

It can be easily found up with

lapply(bb, class)
#$x
#[1] "matrix" "array" 

#$y
#[1] "numeric"

Upvotes: 3

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