Double values of a specific row in a matrix into the next row

Question

I have this matrix a = [nrow = 365, ncol = 288] and I want to double the values of the 59th row. Then it means, the new matrix will be b = [nrow = 366, ncol = 288] and the values of the 59th & 60th row are the same. Is there any quick way to do that without doing the function?

Answer 1

Simply set the row indices, e.g.,

a[c(1:59, 59:365),]

or

a[(k <- seq_len(nrow(a) + 1)) - (k > 59), ]

or

rbind(head(a, 59), tail(a, -58))