Indexing a list element by name and dimension when adding a matrix to a list

Question

I am working within a for loop where each iteration generates a matrix and want to store the resulting matrix within a list. The loop is structured in such a way that I cannot simply index the results list by the loop index, for example ResultsList[[i]] <- ResultsMx will not work is this instance.

Instead, I need to add the ResultsMx to the ResultsList by matching names but am not sure how to index the correct names and deminsions without getting the error: number of items to replace is not a multiple of replacement length

For example, I want to add this matrix

ResultsMx <- structure(c(0.280409, 0.248557, 0.193688, 0.120225, 0.060881, 
                0.03218, 0.029315, 0.019525, 7e-06, 3e-06, 0.306503, 0.240209, 
                0.224629, 0.133996, 0.043117, 0.016981, 0.012545, 0.003268, 7.8e-05, 
                5.8e-05, 0.219001, 0.202018, 0.197539, 0.188427, 0.093204, 0.047265, 
                0.033493, 0.007712, 0.000352, 0.00015, 0.126588, 0.15627, 0.161544, 
                0.194544, 0.171473, 0.103416, 0.070513, 0.014678, 0.001778, 0.000774, 
                0.054797, 0.100531, 0.1249, 0.171576, 0.21895, 0.168987, 0.120546, 
                0.045224, 0.006602, 0.003019, 0.012318, 0.045509, 0.073426, 0.125358, 
                0.225135, 0.219425, 0.169645, 0.117345, 0.030413, 0.011488, 0.000385, 
                0.006894, 0.023663, 0.060295, 0.151452, 0.242802, 0.222163, 0.206509, 
                0.098567, 0.04849, 0, 1.2e-05, 0.000611, 0.005577, 0.035691, 
                0.151408, 0.239021, 0.301288, 0.230251, 0.211833, 0, 0, 0, 2e-06, 
                9.8e-05, 0.017526, 0.098463, 0.245786, 0.417003, 0.724185, 0, 
                0, 0, 0, 0, 9e-06, 0.004297, 0.038665, 0.21495, 0), .Dim = c(10L, 
                                                                             10L))

to this list of blank matrices:

SeasonResults <- list(BHSSummSymScReClass = matrix(0, nrow = 10, ncol = 10),
                      MTGSummSymScReClass = matrix(0, nrow = 10, ncol = 10),
                      BHSWintSymScReClass = matrix(0, nrow = 10, ncol = 10),
                      MTGWintSymScReClass = matrix(0, nrow = 10, ncol = 10)) 

by matching the list element with this object of names:

SeasonNames <- c("BHSSummSymScReClass", "MTGSummSymScReClass")

Here use the following code to match the first list item with the first SeasonName item:

SeasonResults[names(SeasonResults) == SeasonNames[1]] <- ResultsMx

which generates the above warning and only adds the 1,1 element from the ResultsMx .

How can I specify the correct dimensions so that the entire ResultsMx is added to the SeasonResults list based on a name match with SeasonNames ?

I have seen a number of related SO posts, but none that deal with my need to index based on the name match and the dimensions.

Thanks in advance.

Answer 1

We can use a for loop along with the which function. which looks for for where names(SeasonResults) matches those found in SeasonNames . Then we iterate over those indices, replacing the contents with ResultsMx .

for(i in which(names(SeasonResults) %in% SeasonNames)){
    SeasonResults[[i]] <- ResultsMx
}

Answer 2

Just use the current name as element index

SeasonResults[[theName]] = ResultsMx;

for instance

x = list();
x[["a"]] = matrix(1:9, ncol=3);
theName = "b";
x[[theName]] = matrix(letters[1:9], ncol=3);
x;
>  $a
>      [,1] [,2] [,3]
> [1,]    1    4    7
> [2,]    2    5    8
> [3,]    3    6    9
> 
> $b
>      [,1] [,2] [,3]
> [1,] "a"  "d"  "g" 
> [2,] "b"  "e"  "h" 
> [3,] "c"  "f"  "i"