st: A bug in egen and gen?

["Liao, Junlin" <junlin-liao@uiowa.edu>]

I happen to notice a problem with the egen and gen commands. I'm using STATA 2011 SE (64 bit). I do not know if this problem exists in other versions. Please run the following commands to reproduce the problem:

clear
set obs 5
generate y=83085733
generate long z=83085733
egen y_mean=mean(y)
egen z_mean=mean(z)
egen long y_mean_long=mean(y)
egen long z_mean_long=mean(z)
format %10.0g y z  y_mean z_mean y_mean_long z_mean_long
list

By default, both egen and gen command use float for the size of the number and the values generated are not correct. However, if we restrict the numbers to be long integer, we can get correct results.

Anybody else noticed the bug? Is there an explanation for what happens? Thanks,

Junlin Liao




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