[R] calculations on diagonals of a matrix

Griffith Feeney gfeeney at gfeeney.com
Sat May 19 19:42:08 CEST 2001

Given an nxm matrix A I want to compute the nxm matrix B whose ij-th 
element is the sum of the elements of A lying on the diagonal that ends 
with element ij, i.e.,

     b_ij = a_ij + a_(i-1)(j-1) + a_(i-2)(j-2) + ...

In APL (which I no longer use), I would use the 'rotate' operator to derive 
an array whose columns are diagonals of the given array and then cumulate 
down columns. Is there a similar operator in R, or is there another/better way?

r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at stat.math.ethz.ch

More information about the R-help mailing list