How to find the sum of determinant of matrices present inside a list in R?

Question

I am trying to find the sum of determinant of matrices present inside a list using lapply. In the list not all items are a matrix.

I have a list with three elements e.g.

[[1]]
    Sepal.Length Sepal.Width Petal.Length Petal.Width    Species
1            5.1         3.5          1.4         0.2     setosa
2            4.9         3.0          1.4         0.2     setosa
3            4.7         3.2          1.3         0.2     setosa
ETC... 

[[2]]
     [,1] [,2] [,3]
[1,]    1    4    7
[2,]    2    5    8
[3,]    3    6    9

[[3]]
 [1]  1  2  3  4  5  6  7  8  9 10

I am aware I need to check if an item in a list is a matrix using is.matrix() however cannot seem to get this to work.

lapply(list1, function(x){ (is.matrix(x)) })

Returns:

[[1]]
[1] FALSE

[[2]]
[1] TRUE

[[3]]
[1] FALSE

I am unsure where to go from here as I cannot perform det(x) on a list or even element of a list such as the below:

det(list1[2])

Output:

> det(list1[2])
Error in UseMethod("determinant") : 
  no applicable method for 'determinant' applied to an object of class "list"

Any help would greatly be appreciated!

So what is your expected output, based on the sample list you give? Is it a `list` of length equal to your input `list`, with elements equal to the determinant of matrix elements and `NA` else? Or something similar? Please be specific. — Maurits Evers, Aug 28 '22 at 12:41

score 0 · Answer 1 · answered Aug 28 '22 at 12:46

Are you after something like this?

lapply(lst, \(x) {if (is.matrix(x)) det(x) else NA })
#[[1]]
#[1] NA
#
#[[2]]
#[1] 0
#
#[[3]]
#[1] NA

Or if you're only interested in getting the determinant for the 2nd element of lst

det(lst[[2]])
#[1] 0

Note the double square brackets to select a specific element from a list.

Sample data

lst <- list(iris, matrix(1:9, ncol = 3), 1:10)

How to find the sum of determinant of matrices present inside a list in R?

1 Answers1

Sample data