Matrix-exponentiation operator: Difference between revisions

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===Library function call===

<lang R>library(Biodem)

<lang rsplus>library(Biodem)

m <- matrix(c(3,2,2,1), nrow=2)

mtx.exp(m, 0)

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===Infix operator===

The task wants the implementation to be "as an operator". Given that R lets us define new infix operators, it seems fitting to show how to do this. Ideally, for a matrix a and int n, we'd want to be able to use a^n. R actually has this already, but it's not what the task wants:

<lang r>a<-matrix(c(1,2,3,4),2,2)

<lang rsplus>a<-matrix(c(1,2,3,4),2,2)

a^1

a^2</lang>

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[2,] 4 16</pre>

As we can see, it instead returns the given matrix with its elements raised to the nth power. Overwriting the ^ operator would be dangerous and rude. However, R's base library suggests an alternative. %*% is already defined as matrix multiplication, so why not use %^% for exponentiation?

<lang r>`%^%`<-function(mat,n)

<lang rsplus>`%^%`<-function(mat,n)

{

is.wholenumber<-function(x,tol=.Machine$double.eps^0.5){abs(x - round(x))<tol}#See the docs for is.integer