从r中矩阵的每一行中减去一个常数向量 [英] subtract a constant vector from each row in a matrix in r
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问题描述
我有一个5列4行的矩阵.我也有3列的向量.我想分别从矩阵的每一行的第3、4和5列中减去向量中的值.
I have a matrix with 5 columns and 4 rows. I also have a vector with 3 columns. I want to subtract the values in the vector from columns 3,4 and 5 respectively at each row of the matrix.
b <- matrix(rep(1:20), nrow=4, ncol=5)
[,1] [,2] [,3] [,4] [,5]
[1,] 1 5 9 13 17
[2,] 2 6 10 14 18
[3,] 3 7 11 15 19
[4,] 4 8 12 16 20
c <- c(5,6,7)
获得
[,1] [,2] [,3] [,4] [,5]
[1,] 1 5 4 7 10
[2,] 2 6 5 8 11
[3,] 3 7 6 9 12
[4,] 4 8 7 10 13
推荐答案
这正是sweep
的用途:
b <- matrix(rep(1:20), nrow=4, ncol=5)
x <- c(5,6,7)
b[,3:5] <- sweep(b[,3:5],2,x)
b
# [,1] [,2] [,3] [,4] [,5]
#[1,] 1 5 4 7 10
#[2,] 2 6 5 8 11
#[3,] 3 7 6 9 12
#[4,] 4 8 7 10 13
..或什至没有子集或重新分配:
..or even without subsetting or reassignment:
sweep(b,2,c(0,0,x))
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