R:替换随机矩阵的 "off-diagonal"元素

Question

我使用以下代码生成一个随机矩阵，其中一些元素 = 1 在对角线附近，其余元素 = 0。(这基本上是沿着主对角线的随机游走。)

n <- 20
rw <- matrix(0, ncol = 2, nrow = n)
indx <- cbind(seq(n), sample(c(1, 2), n, TRUE))
rw[indx] <- 1
rw[,1] <- cumsum(rw[, 1])+1
rw[,2] <- cumsum(rw[, 2])+1
rw2 <- subset(rw, (rw[,1] <= 10 & rw[,2] <= 10))
field <- matrix(0, ncol = 10, nrow = 10)
field[rw2] <- 1
field

     [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
 [1,]    0    1    1    1    0    0    0    0    0     0
 [2,]    0    0    0    1    0    0    0    0    0     0
 [3,]    0    0    0    1    0    0    0    0    0     0
 [4,]    0    0    0    1    1    1    1    0    0     0
 [5,]    0    0    0    0    0    0    1    1    0     0
 [6,]    0    0    0    0    0    0    0    1    0     0
 [7,]    0    0    0    0    0    0    0    1    0     0
 [8,]    0    0    0    0    0    0    0    1    1     1
 [9,]    0    0    0    0    0    0    0    0    0     0
[10,]    0    0    0    0    0    0    0    0    0     0

下一步，我想将 1 元素右侧/上侧的 0 元素替换为 1。对于上述矩阵，所需的输出将是:

     [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
 [1,]    0    1    1    1    1    1    1    1    1     1
 [2,]    0    0    0    1    1    1    1    1    1     1
 [3,]    0    0    0    1    1    1    1    1    1     1
 [4,]    0    0    0    1    1    1    1    1    1     1
 [5,]    0    0    0    0    0    0    1    1    1     1
 [6,]    0    0    0    0    0    0    0    1    1     1
 [7,]    0    0    0    0    0    0    0    1    1     1
 [8,]    0    0    0    0    0    0    0    1    1     1
 [9,]    0    0    0    0    0    0    0    0    0     0
[10,]    0    0    0    0    0    0    0    0    0     0

我已经尝试过

fill <- function(row) {first = match(1, row); if (is.na(first)) {row = rep(1, 10)} else {row[first:10] = 1}; return(row)}  
field2 <- apply(field, 1, fill)
field2

但这给了我:

      [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
 [1,]    0    0    0    0    0    0    0    0    1     1
 [2,]    1    0    0    0    0    0    0    0    1     1
 [3,]    1    0    0    0    0    0    0    0    1     1
 [4,]    1    1    1    1    0    0    0    0    1     1
 [5,]    1    1    1    1    0    0    0    0    1     1
 [6,]    1    1    1    1    0    0    0    0    1     1
 [7,]    1    1    1    1    1    0    0    0    1     1
 [8,]    1    1    1    1    1    1    1    1    1     1
 [9,]    1    1    1    1    1    1    1    1    1     1
[10,]    1    1    1    1    1    1    1    1    1     1

谁能帮我解决这个问题吗？

干杯，

MCE

PS:如果第一行全为零(上面的代码可能会发生这种情况)，则应将其更改为全零。

Answer 1

为什么不只是:

t(apply(field,1,cummax))

一个实例:

dput(field)
structure(c(0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 
0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 
0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 
0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 
0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0), .Dim = c(10L, 
10L))

> field
      [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
 [1,]    0    0    0    0    0    0    0    0    0     0
 [2,]    1    1    1    1    1    1    0    0    0     0
 [3,]    0    0    0    0    0    1    0    0    0     0
 [4,]    0    0    0    0    0    1    0    0    0     0
 [5,]    0    0    0    0    0    1    1    1    1     1
 [6,]    0    0    0    0    0    0    0    0    0     0
 [7,]    0    0    0    0    0    0    0    0    0     0
 [8,]    0    0    0    0    0    0    0    0    0     0
 [9,]    0    0    0    0    0    0    0    0    0     0
[10,]    0    0    0    0    0    0    0    0    0     0

输出:

> t(apply(field,1,cummax))
      [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
 [1,]    0    0    0    0    0    0    0    0    0     0
 [2,]    1    1    1    1    1    1    1    1    1     1
 [3,]    0    0    0    0    0    1    1    1    1     1
 [4,]    0    0    0    0    0    1    1    1    1     1
 [5,]    0    0    0    0    0    1    1    1    1     1
 [6,]    0    0    0    0    0    0    0    0    0     0
 [7,]    0    0    0    0    0    0    0    0    0     0
 [8,]    0    0    0    0    0    0    0    0    0     0
 [9,]    0    0    0    0    0    0    0    0    0     0
[10,]    0    0    0    0    0    0    0    0    0     0