In a previous blog post about computing confidence intervals for rankings, I inadvertently used the VAR function in SAS/IML 9.22, without providing equivalent functionality for those readers who are running an earlier version of SAS/IML software. (Thanks to Eric for pointing this out.)

If you are using a version of SAS/IML prior 9.22, the following module computes the variance of each column of a matrix, and correctly handles missing values in the data:

/** Var: return sample variance of each column of a data matrix **/ /** For this module x is a matrix that contains the data **/ start Var(x); mean = x[:,]; countn = j(1, ncol(x)); /** allocate vector for counts **/ do i = 1 to ncol(x); /** count nonmissing values **/ countn[i] = sum(x[,i]^=.); /** in each column **/ end; var = (x-mean)[##,] / (countn-1); return ( var ); finish; |

This module appears in Appendix D of my book, *Statistical Programming with SAS/IML Software*.

## 3 Comments

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This is calculating the variance of each column of the matrix but I am not getting any sort of output.

Is it just in my log? how to I get the variance to show up in an output/results form?

You can print the matrix to display its contents:

v = var(x);

print v;