# st: Stata drops variables in the dataset

 From "Can Huang" To Subject st: Stata drops variables in the dataset Date Wed, 30 Nov 2005 11:58:49 -0000

```Dear StataList Members:

I can not find the answer to the problem of "Stata drops variables in the
dataset" in the on-line resources. Maybe it is too basic to you fellow
members. I find it is different from "Why do estimation commands sometimes
drop variables?" in http://www.stata.com/support/faqs/stat/drop.html.

I run a estimation command with some different options. After the first time
of running the command, Stata randomly drops variable in the dataset. I then
have to exit and re-enter to run the command again. An example is below. It
happens frequently.

Could any colleague kindly point out the place where I can find the remedy
measures?

Thanks for your abundant knowledge and experience in advance!

Can Huang

xtgls tfp rdper rdexp newprodin fixassetin, i(number) t(year)

Cross-sectional time-series FGLS regression

Coefficients:  generalized least squares
Panels:        homoskedastic
Correlation:   no autocorrelation

Estimated covariances      =         1          Number of obs      =
57
Estimated autocorrelations =         0          Number of groups   =
2
Estimated coefficients     =         5          Obs per group: min =
28
avg =
28.5
max =
29
Wald chi2(4)       =
0.94
Log likelihood             =  81.86981          Prob > chi2        =
0.9192

----------------------------------------------------------------------------
--
tfp |      Coef.   Std. Err.      z    P>|z|     [95% Conf.
Interval]
-------------+--------------------------------------------------------------
--
rdper |    .000026    .000034     0.76   0.445    -.0000407
0000927
rdexp |   .0008324   .0013939     0.60   0.550    -.0018996
0035644
newprodin |  -.0238213   .0744405    -0.32   0.749    -.1697219
1220793
fixassetin |   .0001438   .0005998     0.24   0.811    -.0010317
0013193
_cons |  -.0172437   .0113719    -1.52   0.129    -.0395321
0050447
----------------------------------------------------------------------------
--

xtgls tfp rdper rdexp newprodin fixassetin, i(number) t(year)
panels(heterosk
> edastic)