Adding two data frames of different sizes and subsets

Question

I have a bunch of transition matrices that look like these.

> temp
        31-60 5-30 61-90 Current PaidOff
5-30      283  317     9     500       9
Current     0 2935     0  179989    1689
PaidOff     0    0     0       0       0

I want to standardize the size so I've made a 0 matrix with the correct row and column names:

> blankMatrix
                  Current 5-30 31-60 61-90 91-120 ChargeOff_Default PaidOff
Current                 0    0     0     0      0                 0       0
5-30                    0    0     0     0      0                 0       0
31-60                   0    0     0     0      0                 0       0
61-90                   0    0     0     0      0                 0       0
91-120                  0    0     0     0      0                 0       0
ChargeOff_Default       0    0     0     0      0                 0       0
PaidOff                 0    0     0     0      0                 0       0

Is there a way to easily add the first matrix to the second. So for instance the number 283 would go into position (2,3) automatically. I'm hoping to avoid a long and messy for loop where I constantly iterate and check if the row and column names match.

Thank you!

Answer 1

You can create a matrix of row and column index from the row and column names of temp using expand.grid and then blankMatrix[matrix index] will select values from the index pair in the matrix index; To change the values at the corresponding index, just assign the values to it;

temp <- as.matrix(temp)
blankMatrix <- as.matrix(blankMatrix)

matIndex <- as.matrix(expand.grid(rownames(temp), colnames(temp)))
blankMatrix[matIndex] <- temp
blankMatrix
#                  Current X5.30 X31.60 X61.90 X91.120 ChargeOff_Default PaidOff
#Current            179989  2935      0      0       0                 0    1689
#5-30                  500   317    283      9       0                 0       9
#31-60                   0     0      0      0       0                 0       0
#61-90                   0     0      0      0       0                 0       0
#91-120                  0     0      0      0       0                 0       0
#ChargeOff_Default       0     0      0      0       0                 0       0
#PaidOff                 0     0      0      0       0                 0       0