How to get rid of dim1, dim2, ... on top of my matrix?-CodePudding

I have a matrix called AS (in R) that collects indices of elements of an array that satisfy a certain condition. This matrix AS, however, is labeled at the top by dim1, dim2, ... which prevent me from using those indexes in typical expressions (cf. picture below). How do I get rid of these dim labels and convert this collection of indices to a regular usable matrix?

Here’s how my dim-labeled matrix looks:

And the error if I try to use the indices contained here normally:

Note: it’s not the dimensions that are incorrect here since RandPoints[1, ...] is supposed to accept 4 arguments for “...” E.g., it runs fine if I type in RandPoints[1,12,1,1,1], but I rather want that [12,1,1,1] to be supplied by calling the first row of AS as attempted in the picture.

CodePudding user response：

We could use colnames(my_matrix) <- NULL. Here is an example:

# create a matrix
my_matrix<-matrix(1:30,ncol=3)

# assign names to your matrix
colnames(my_matrix)<-c("dim1", "dim2", "dim3")

# remove the column names
colnames(my_matrix) <- NULL

my_matrix

      [,1] [,2] [,3]
 [1,]    1   11   21
 [2,]    2   12   22
 [3,]    3   13   23
 [4,]    4   14   24
 [5,]    5   15   25
 [6,]    6   16   26
 [7,]    7   17   27
 [8,]    8   18   28
 [9,]    9   19   29
[10,]   10   20   30

CodePudding user response：

We may need to pass a matrix of index for subsetting. One option is to convert the matrix row to list with as.list and then cbind so that it becomes a matrix of one row with 5 columns. The 1 is concatenated with the 4 elements of the 2nd row of 'AS' and converted to list

RandPoints[do.call(cbind, as.list(c(1, AS[2,])))]

Or another option is cbind. Note that for matrix/data.frame, the default option is drop = TRUE when there is a single row/column which converts the matrix to a vector. So, change it to drop = FALSE and cbind with 1 (to return 5 column matrix)

 RandPoints[cbind(1, AS[2,, drop = FALSE])]

data

AS <- cbind(dim2 = c(3, 5), dim3 = c(1, 1), dim4 = c(1, 1), dim5 = c(1, 1))
 RandPoints <- array(1:750, dim = c(5, 5, 5, 2, 3))