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Array: subtract by line

How can I subtract the vector of each row in an array?

a <- array(1:8, dim=c(2,2,2)) a , , 1 [,1] [,2] [1,] 1 3 [2,] 2 4 , , 2 [,1] [,2] [1,] 5 7 [2,] 6 8

Using apply gives me:

 apply(a,c(1,2), '-',c(1,5)) , , 1 [,1] [,2] [1,] 0 1 [2,] 0 1 , , 2 [,1] [,2] [1,] 2 3 [2,] 2 3

I am trying to get:

 , , 1 [,1] [,2] [1,] 0 -2 [2,] 1 -1 , , 2 [,1] [,2] [1,] 4 2 [2,] 5 3

Thanks in advance for any tips.

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4 answers

Use sweep to work with a specific field of the array: rows are the second dimension (margin).

 sweep(a,MARGIN=2,c(1,5),FUN="-")
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 > library (plyr) > aaply(a, 1, "-", c(1,5) ) , , = 1 X1 1 2 1 0 -2 2 1 -1 , , = 2 X1 1 2 1 4 2 2 5 3
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Use scale to subtract either the average or the specified vector from each row, and then divide it by either the standard deviation or the specified vector.

In your example: scale(a, c(1,5), FALSE)

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 > a - rep(c(1,5),each=2) , , 1 [,1] [,2] [1,] 0 -2 [2,] 1 -1 , , 2 [,1] [,2] [1,] 4 2 [2,] 5 3
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