填写R中的矩阵列表

Question

I want to give a constant columns value to every matrices in a list of matrices. Here is the list of matrices.

list_matrix_Tanzania_Mod <- lapply(1:4, function(i)
                             matrix(sample(1:50, 4*10, replace=TRUE),
                                 ncol=4, dimnames=list(NULL, LETTERS[1:4])))

Here is one matrix's example.

[[1]]
       A  B  C  D
 [1,] 15 31  5 16
 [2,] 12 19 28 12
 [3,] 36 34 37 19
 [4,] 26 34  7  8
 [5,] 34 17 12 47
 [6,] 47 46 35 11
 [7,] 14 10  4 37
 [8,] 39  3 30 32
 [9,] 41 26 32 35
[10,] 13  7  3 49

I want the column D in each matrices to get the values Modis500_2000 instead of the numbers.

I also want the column C to be equal to AB. For instance, in the matrix example above, I want the column C in the row one to get the value 1531 instead of 5.

Answer 1

I read your previous question ( Add new columns to every matrices in a list of matrices in R ) and I would highly suggest that you switch to using data.frames instead of matrices. It is in my opinion a better data structure for your type of work. Then you can use a function like transform to add/modify columns, in a rather simple and intuitive way:

list_matrix_Tanzania_Mod <- lapply(list_matrix_Tanzania_Mod,
                                   transform,
                                   C = A * B,
                                   D = Modis500_2000,
                                   E = A + B)

This will modify two columns ( C and D ) and add one ( E ).

If you ever need to convert your data back to matrices, then you can do:

list_matrix_Tanzania_Mod <- lapply(list_matrix_Tanzania_Mod,
                                   data.matrix)