Sapply function for element-wise calculation a matrix in R

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I have an (5x4) matrix in R, namely data defined as follows:

set.seed(123)    
data <- matrix(rnorm(5*4,mean=0,sd=1), 5, 4)

and I want to create 4 different matrices that follows this formula: Assume that data[,1] = [A1,A2,A3,A4,A5]. I want to create the following matrix:

        A1-A1 A1-A2 A1-A3 A1-A4 A1-A5 
        A2-A1 A2-A2 A2-A3 A2-A4 A2-A5
   G1 = A3-A1 A3-A2 A3-A3 A3-A4 A3-A5
        A4-A1 A4-A2 A4-A3 A4-A4 A4-A5
        A5-A1 A5-A2 A5-A3 A5-A4 A5-A5

Similarly for the other columns i want to calculate at once all the G matrices (G1,G2,G3,G4). How can i achieve that with the sapply funciton?

sapply apply r matrix loops
1 Answers

We may use elementwise subtraction of column with outer

outer(data[,1], data[,1], `-`)

If it should be done on each column, loop over the columns (or do asplit with MARGIN = 2 to split by column), loop over the list and apply the outer

lapply(asplit(data, 2), function(x) outer(x, x, `-`))
user_37322710
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