CODEWITHSUNDEEP
rmatrixcbind
DR15
DR15

Reputation: 693

How to insert 'n' columns in a matrix

Suppose I have the following matrix

A = diag(5)
A
     [,1] [,2] [,3] [,4] [,5]
[1,]    1    0    0    0    0
[2,]    0    1    0    0    0
[3,]    0    0    1    0    0
[4,]    0    0    0    1    0
[5,]    0    0    0    0    1

and I want to add the first column of the matrix A in the new_A (for n times, suppose that n = 3, but in my case, n can be bigger)

new_A
     [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8]
[1,]    1    1    1    1    0    0    0    0
[2,]    0    0    0    0    1    0    0    0
[3,]    0    0    0    0    0    1    0    0
[4,]    0    0    0    0    0    0    1    0
[5,]    0    0    0    0    0    0    0    1

How can I add the first column of the A for n times in the new_A automatically?

Upvotes: 0

Views: 44

Answers (1)

Ronak Shah
Ronak Shah

Reputation: 389135

Repeat 1 n times and append the remaining columns. 

n = 3
A[, c(rep(1, n + 1), 2:ncol(A))]

#     [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8]
#[1,]    1    1    1    1    0    0    0    0
#[2,]    0    0    0    0    1    0    0    0
#[3,]    0    0    0    0    0    1    0    0
#[4,]    0    0    0    0    0    0    1    0
#[5,]    0    0    0    0    0    0    0    1

Upvotes: 1

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