[R] converting MATLAB -> R | element-wise operation
Evan Cooch
ev@n@cooch @end|ng |rom gm@||@com
Tue Feb 27 20:54:26 CET 2024
So, trying to convert a very long, somewhat technical bit of lin alg
MATLAB code to R. Most of it working, but raninto a stumbling block that
is probaably simple enough for someone to explain.
Basically, trying to 'line up' MATLAB results from an element-wise
division of a matrix by a vector with R output.
Here is a simplified version of the MATLAB code I'm translating:
NN = [1, 2, 3; 4, 5, 6]; % Example matrix
lambda = [2, 3, 4]; % Example vector
result_matlab = NN ./ lambda;
which yields
0.50000 0.66667 0.75000
2.00000 1.66667 1.50000
So, the only way I have stumbled onto in R to generate the same results
is to use 'sweep'. The following 'works', but I'm hoping someone can
explain why I need something as convoluted as this seems (to me, at least).
NN <- matrix(c(1, 2, 3, 4, 5, 6), nrow = 2, byrow = TRUE) # Example matrix
lambda <- c(2, 3, 4) # Example vector
sweep(NN, 2, lambda, "/")
[,1] [,2] [,3]
[1,] 0.5 0.6666667 0.75
[2,] 2.0 1.6666667 1.50
First tried the more 'obvious' NN/lambda, but that yields 'the wrong
answer' (based solely on what I'm trying to accomplish):
[,1] [,2] [,3]
[1,] 0.500000 0.5 1.0
[2,] 1.333333 2.5 1.5
So, why 'sweep'?
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