I think that this is an easy one...
I have a matrix where each row is an (x,y,z) triplet. Given a potential
(xnew,ynew,znew) triplet I want to know if the matrix already contains a
row with the new values (the space already has that point). I can do it
using a for loop, but I would like to know
Try something like:
x1 - matrix(sample(1:5, 30, replace=TRUE), ncol=3)
x2 - x1[4,]
which(colSums(abs(t(x1) - x2)) == 0)
[1] 4
Note: If the data are not all integers, you probably should test whether
the absolute sum differences is less than some very small number, rather
than == 0.
This
