Insert row at a specific location in matrix using R

Question

I'm trying to add rows to a matrix at particular locations, where the locations are contained in a vector. The schema below shows the inputs and the expected outcome. I tried to use a "for" loop but couldn't make it work. Any suggestions help.

Source Matrix (6x3)

(1) 1   2   3
(2) 4   5   6
(3) 7   8   9
(4) 6   9   2
(5) 3   6   1
(6) 2   2   7

Vector of locations (indicates the row in the source matrix that will contain zeros)

[2, 5, 6]  

Result Matrix(6+length.vector x 3)

(1) 1   2   3
(2*)0   0   0
(3) 4   5   6
(4) 7   8   9
(5*)0   0   0
(6*)0   0   0
(7) 6   9   2
(8) 3   6   1
(9) 2   2   7

Answer 1

mat <- matrix(1:18,6)
vec <- c(2, 5, 6)

# New matrix 'new_mat' with all zeros, 
# No. of rows = original matrix rows + number new rows to be added
new_mat <- matrix(0,nrow=9,ncol=3)  

# 'new_mat' rows getting filled with `mat` values
new_mat[-vec,] <- mat   
new_mat
#      [,1] [,2] [,3]
# [1,]    1    7   13
# [2,]    0    0    0
# [3,]    2    8   14
# [4,]    3    9   15
# [5,]    0    0    0
# [6,]    0    0    0
# [7,]    4   10   16
# [8,]    5   11   17
# [9,]    6   12   18