所以我看到很多关于通过一些简单的矩阵索引来改变矩阵中小于一定数量等于零的所有值的帖子。但是我认为我所拥有的是更先进的，我遇到了一些麻烦所以希望你们能帮忙。这是我正在使用的代码：
x <- (1:5)
y <- c(0,10,0,0,8)
n <- 12
mat <- t(sapply(y, function(test) pmax(seq(test, (test-n+1), -1), 0) ))
mat
这会产生：
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [,11] [,12]
[1,] 0 0 0 0 0 0 0 0 0 0 0 0
[2,] 10 9 8 7 6 5 4 3 2 1 0 0
[3,] 0 0 0 0 0 0 0 0 0 0 0 0
[4,] 0 0 0 0 0 0 0 0 0 0 0 0
[5,] 8 7 6 5 4 3 2 1 0 0 0 0
xmat <- replicate(ncol(mat),x)
然后我想找到哪个y不等于零，然后将xmat中的值替换为零，直到mat等于零，然后将值更改为x值。以下是我目前的情况。
CountTest <- which(y != 0)
xmat[CountTest,] <- apply(xmat[CountTest,], 1, function(xu) ifelse(xu > 0, 0, xu))
xmat
这会产生：
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [,11] [,12]
[1,] 1 1 1 1 1 1 1 1 1 1 1 1
[2,] 0 0 0 0 0 0 0 0 0 0 0 0
[3,] 3 3 3 3 3 3 3 3 3 3 3 3
[4,] 4 4 4 4 4 4 4 4 4 4 4 4
[5,] 0 0 0 0 0 0 0 0 0 0 0 0
所需的输出是：
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [,11] [,12]
[1,] 1 1 1 1 1 1 1 1 1 1 1 1
[2,] 0 0 0 0 0 0 0 0 0 0 2 2
[3,] 3 3 3 3 3 3 3 3 3 3 3 3
[4,] 4 4 4 4 4 4 4 4 4 4 4 4
[5,] 0 0 0 0 0 0 0 0 5 5 5 5
答案 0 :(得分：1)
你可以尝试
> xmat*(mat==0)
# [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [,11] [,12]
#[1,] 1 1 1 1 1 1 1 1 1 1 1 1
#[2,] 0 0 0 0 0 0 0 0 0 0 2 2
#[3,] 3 3 3 3 3 3 3 3 3 3 3 3
#[4,] 4 4 4 4 4 4 4 4 4 4 4 4
#[5,] 0 0 0 0 0 0 0 0 5 5 5 5