I would like to transform a vector of integer such:
vector = c(0,6,1,8,5,4,2)
length(vector) = 7
max(vector) = 8
into a matrix m of nrow = length(vector) and ncol = max(vector):
m =
0 0 0 0 0 0 0 0
1 1 1 1 1 1 0 0
1 0 0 0 0 0 0 0
1 1 1 1 1 1 1 1
1 1 1 1 1 0 0 0
1 1 1 1 0 0 0 0
1 1 0 0 0 0 0 0
It's just an example of what I am trying to do. I intend that the function work with every vector of integer.
I tried to used the function mapply(rep, 1, vector) but I obtained a list and I didn't succeed to convert it into a matrix...
It would be very useful for me if someone can help me.
Best Regards,
Maxime
If you use c(rep(1, x), rep(0, max(vector-x))
on each element of your variable vector
you get the desired binary results. Looping that with sapply
even returns a matrix. You only need to transpose it afterwards and you get your result.
vector = c(0,6,1,8,5,4,2)
result <- t(sapply(vector, function(x) c(rep(1, x), rep(0, max(vector)-x))))
is.matrix(result)
#> [1] TRUE
result
#> [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8]
#> [1,] 0 0 0 0 0 0 0 0
#> [2,] 1 1 1 1 1 1 0 0
#> [3,] 1 0 0 0 0 0 0 0
#> [4,] 1 1 1 1 1 1 1 1
#> [5,] 1 1 1 1 1 0 0 0
#> [6,] 1 1 1 1 0 0 0 0
#> [7,] 1 1 0 0 0 0 0 0
Putting that into a function is easy:
binaryMatrix <- function(v) {
t(sapply(v, function(x) c(rep(1, x), rep(0, max(v)-x))))
}
binaryMatrix(vector)
# same result as before
Created on 2021-02-14 by the reprex package (v1.0.0)
Another straightforward approach would be to exploit matrix sub-assignment using row/column indices in a matrix form (see, also, ?Extract
).
Define a matrix of 0s:
x = c(0, 6, 1, 8, 5, 4, 2)
m = matrix(0L, nrow = length(x), ncol = max(x))
And fill with 1s:
i = rep(seq_along(x), x) ## row indices of 1s
j = sequence(x) ## column indices of 1s
ij = cbind(i, j)
m[ij] = 1L
m
# [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8]
#[1,] 0 0 0 0 0 0 0 0
#[2,] 1 1 1 1 1 1 0 0
#[3,] 1 0 0 0 0 0 0 0
#[4,] 1 1 1 1 1 1 1 1
#[5,] 1 1 1 1 1 0 0 0
#[6,] 1 1 1 1 0 0 0 0
#[7,] 1 1 0 0 0 0 0 0
Assuming that all values in the vector are non-negative integers, you can define the following function
transformVectorToMatrix <- function(v) {
nrOfCols <- max(v)
zeroRow <- integer(nrOfCols)
do.call("rbind",lapply(v,function(nrOfOnes) {
if(nrOfOnes==0) return(zeroRow)
if(nrOfOnes==nrOfCols) return(zeroRow+1)
c(integer(nrOfOnes)+1,integer(nrOfCols-nrOfOnes))
}))
}
and finally do
m = transformVectorToMatrix(vector)
to get your desired binary matrix.
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