Posts Tagged ‘ matrixManipulation ’

Calculating distances (across matrices)

October 5, 2012
By
Calculating distances (across matrices)

This Gist is mostly for my future self, as a reminder of how to find distances between each row in two different matrices. To create a distance matrix from a single matrix, the function dist(), from the stats package is sufficient. There are times, ho...

Read more »

Log odds ratios and an indicator matrix from categorical data

October 4, 2012
By
Log odds ratios and an indicator matrix from categorical data

A long title, but there are a couple of handy things in this Gist. The first, and more obscure, is the conversion of a data.frame of categorical variables into a matrix of dummy/binary/indicator variables, one for each category of each original variab...

Read more »

Modifying select off-diagonal items in a matrix

September 25, 2012
By

This is something I have had the occasion to do, and never remember how, so this is legitimately a reminder to my future self of how to do things with off-diagonal elements of a matrix. Select rows and columns are easy: mat or mat, for...

Read more »