See Proc Standard for easy way to mean-fill.

On Fri, 08 Oct 1999 16:09:02 -0700, David Cassell <cassell@mail.cor.epa.gov> wrote:

>JGerstle@SW.UA.EDU wrote: >> >> I haven't had any luck finding a solution to this in the manuals. >> Hopefully someone can help. >> >> Using SAS 6.12 on Win95, I need to run several PROC CORR >> ALPHA on a dataset with several missing values spread throughout >> it. According to the SAS Log, it's recommended to use NOMISS >> when calculating ALPHA. This is fine, except it leaves us with a >> low n. We would like to replace each missing value with the mean >> of that variable. Is there an option within PROC CORR or another >> PROC to do this automatically or will I have to calculate the means >> beforehand and run a data step to replace the missing values. I >> have around 40 odd variables so I'd rather do the former than the >> latter. > >It's straightforward to do. One way is via PROC SQL. >Another is to use PROC SUMMARY or PROC MEANS to get the means >in a new dataset and combine the info. But I'm not writing >any code here, because I want to say this: > >This is a bad idea in many cases. Please do not impute >data like this unless you can show that this is going to >be valid, and will not drive the results [as appears likely >given your concern about small n]. > >Try a few plots for yourself. Take a nice dataset you have >already, say n=50, and plot X vs Y. Look at the statistics. >Now replace half the X's with the mean of X, and redo. >You may see an enormous difference. It will fluctuate >depending on the data. > >So don't do this if you can possibly avoid it. > >David >-- >David Cassell, OAO cassell@mail.cor.epa.gov >Senior computing specialist >mathematical statistician