How use sapply() to construct this matrix difference operator in R

Question

How to use apply function in R to construct a matrix difference operator just like matrix B? I created a 3x4 matrix B0 with all elements 0 and tried to change the diagonal elements, but it does not work. My code is apply(B0, function(x) diag(x)=1), and how could I correct it?

Answer 1

If the question is how to produce the matrix shown in the image that appears when you click on the text in the question then here are several ways:

diff(diag(4))
##      [,1] [,2] [,3] [,4]
## [1,]   -1    1    0    0
## [2,]    0   -1    1    0
## [3,]    0    0   -1    1

apply(diag(4), 1, diff)
##      [,1] [,2] [,3] [,4]
## [1,]   -1    1    0    0
## [2,]    0   -1    1    0
## [3,]    0    0   -1    1

sapply(as.data.frame(diag(4)), diff)
##      V1 V2 V3 V4
## [1,] -1  1  0  0
## [2,]  0 -1  1  0
## [3,]  0  0 -1  1

sapply(1:4, function(i) diff(diag(4)[, i]))
##      [,1] [,2] [,3] [,4]
## [1,]   -1    1    0    0
## [2,]    0   -1    1    0
## [3,]    0    0   -1    1