Calculate weighted mean from matrix in R - r

Question

I have a matrix that looks like the following. For rows 1:23, I would like to calculate the weighted mean, where the data in rows 1:23 are the weights and row 24 is the data.
1 107 33 41 22 12 4 122 44 297 123 51 16 7 9 1 1 0
10 5 2 2 1 0 3 4 6 12 3 3 0 1 1 0 0 0
11 1 3 1 0 0 0 4 2 8 3 4 0 0 0 0 0 0
12 2 1 1 0 0 0 2 1 5 6 3 1 0 0 0 0 0
13 1 0 1 0 0 0 3 1 3 5 2 2 0 1 0 0 0
14 3 0 0 0 0 0 3 1 2 3 0 1 0 0 0 0 0
15 0 0 0 0 0 0 2 0 0 1 0 1 0 0 0 0 0
16 0 0 0 0 1 0 0 0 2 0 0 0 0 0 0 0 0
17 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0
18 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
19 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0
2 80 27 37 5 6 4 97 48 242 125 44 27 7 8 8 0 2
20 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0
21 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0
22 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0
23 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0
3 47 12 33 12 6 1 63 42 200 96 45 19 6 6 9 2 0
4 45 14 21 9 4 2 54 26 130 71 36 17 8 5 1 0 2
5 42 10 14 6 3 2 45 19 89 45 26 7 4 8 2 1 0
6 17 3 12 5 2 0 18 21 51 41 19 15 5 1 1 0 0
7 16 2 6 0 0 1 14 9 37 23 17 7 3 0 3 0 0
8 9 4 4 2 1 0 7 9 30 15 8 3 3 1 1 0 1
9 12 2 3 1 1 1 6 5 14 12 5 1 2 0 0 1 0
24 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
As an example using the top two rows, there would have an additional column at the end indicated the weighted mean.
1 107 33 41 22 12 4 122 44 297 123 51 16 7 9 1 1 0 6.391011
10 5 2 2 1 0 3 4 6 12 3 3 0 1 1 0 0 0 6.232558
I'm a little new to coding so I wasn't too sure how to do it - any advice would be appreciated!

Answer 1

You can do:
apply(df[-nrow(df), ], 1, function(row) weighted.mean(df[nrow(df), ], row))

Answer 2

I'm assuming your first columns is some kind of index and not used for the weighted mean (and the data is stored in matr_dat):
apply(matr_dat[-nrow(matr_dat), -1], 1,
function(row) weighted.mean(matr_dat[nrow(matr_dat), -1], row))
Using apply and setting the margin to 1, the function defined in the third argument of apply to each row of the data; to calculate the weighted mean, you can use weighted.mean and set the weights to the values of the row.