How can I delete columns of a matrix based on row values in R?

Question

In this square matrix I want to look up all non-zero values in the first column and delete the columns that corresponds to the row names of the non-zero values. Then I want to look up the next not deleted column and repeat the same process, and repeat this till I reached the last column. Any advice?

Matrix example

added an example that is not a picture

newt <- matrix(c(0,1,0,0,1,0,0,1,0,0,0,1,0,1,0,1), nrow = 4, ncol = 4)
colnames(newt) <- c("1", "2", "3", "4")

only columns 1 and 3 should be retained

Answer 1

You can take help of this while loop:

rowname <- rownames(newt)
vec <- colnames(newt)
i <- 1
col <- vec[i]

while(i < length(vec)) {
  vec <- setdiff(vec, rowname[newt[, col] == 1])
  i <- i + 1
  col <- vec[i]
}
result <- newt[, vec]
result

#  1 3
#1 0 0
#2 1 0
#3 0 0
#4 0 1

data

newt <- matrix(c(0,1,0,0,1,0,0,1,0,0,0,1,0,1,0,1), nrow = 4, ncol = 4)
colnames(newt) <- c("1", "2", "3", "4")
rownames(newt) <- c("1", "2", "3", "4")