CODEWITHSUNDEEP
rmatrixmultiplication
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Reputation: 1295

Multiply each element in a vector by itself to create a matrix

I'm trying to multiply each element in a vector by itself such that it produces a matrix that is symmetric about the diagonal. For example, given this vector::

x <- 1:3

I would like to create this:

1 2 3  
2 4 6 
3 6 9

i.e:

x[1]*x[1] x[2]*x[1] x[3]*x[1]  
x[1]*x[2] x[2]*x[2] x[3]*x[2] 
x[1]*x[3] x[2]*x[3] x[3]*x[3]

Any help would be greatly appreciated. Thanks.

Upvotes: 6

Views: 2608

Answers (1)

flodel
flodel

Reputation: 89097

Like this:

x %o% x

which is a shortcut for

outer(x, x)

You can also do

 tcrossprod(x)

Upvotes: 10

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