Is there a way to use apply family functions instead of the for loop in the code below?
m <- matrix(0, 10, 5)
m
for (i in 2:5) m[,i] <- m[,(i-1)] + 1
m
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not really (although I can imagine someone will come up with something clever ...) – Ben Bolker Oct 14 '20 at 16:16
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@BenBolker Why not? – Joan Oct 14 '20 at 16:32
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```invisible(lapply(2:5, function(i) m[,i] <<- m[,(i-1)] + 1)); m``` – M-- Oct 14 '20 at 16:54
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1because the `apply` family is not really designed for sequential operation. – Ben Bolker Oct 14 '20 at 16:58
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@M-- I tried too sapply(2:7, function(i) mm[,i] <<- mm[,(i-1)] + 1) and it works. – Joan Oct 14 '20 at 17:05
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when looping over a vector (``2:5``), sapply and lapply are not that different. – M-- Oct 14 '20 at 17:06
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@M-- What does <<- mean? – Joan Oct 14 '20 at 17:09
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[What does <<- mean in R?](https://stackoverflow.com/q/13273002) – M-- Oct 14 '20 at 17:11
1 Answers
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Does this answer:
> t(apply(m, 1, function(x) x = 0:4))
[,1] [,2] [,3] [,4] [,5]
[1,] 0 1 2 3 4
[2,] 0 1 2 3 4
[3,] 0 1 2 3 4
[4,] 0 1 2 3 4
[5,] 0 1 2 3 4
[6,] 0 1 2 3 4
[7,] 0 1 2 3 4
[8,] 0 1 2 3 4
[9,] 0 1 2 3 4
[10,] 0 1 2 3 4
>
Data used:
> m
[,1] [,2] [,3] [,4] [,5]
[1,] 0 0 0 0 0
[2,] 0 0 0 0 0
[3,] 0 0 0 0 0
[4,] 0 0 0 0 0
[5,] 0 0 0 0 0
[6,] 0 0 0 0 0
[7,] 0 0 0 0 0
[8,] 0 0 0 0 0
[9,] 0 0 0 0 0
[10,] 0 0 0 0 0
> for(i in 2:5) m[,i] <- m[,(i-1)] + 1
> m
[,1] [,2] [,3] [,4] [,5]
[1,] 0 1 2 3 4
[2,] 0 1 2 3 4
[3,] 0 1 2 3 4
[4,] 0 1 2 3 4
[5,] 0 1 2 3 4
[6,] 0 1 2 3 4
[7,] 0 1 2 3 4
[8,] 0 1 2 3 4
[9,] 0 1 2 3 4
[10,] 0 1 2 3 4
>
Karthik S
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Thanks for your proposal. I wanted to loop over the columns of the matrix. – Joan Oct 14 '20 at 16:46
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