Dear Statalisters,

I am exporting regression tables using esttad with additional lines of stored values (which I store using estadd local as shown below). My data is panel of district level variables. How can I create a local that counts the number of distinct districts included in each regression?

Please find below the codes I have been using as well as the sample dataset.

Code:
qui eststo: reghdfe y x1, absorb(district year province#year) vce(cluster district)
        su y if e(sample), mean 
        loc mymean: di %8.2f r(mean)     
                                estadd loc mD `mymean', replace                            
                                estadd loc districtfe "YES", replace
                                estadd loc yearfe "YES", replace
                                estadd loc provinceyearfe "YES", replace
                                estadd loc controls "NO", replace    
                  
esttab using "$tables\outputfile.tex", se r2 label compress replace obslast depvars nocons ///
            keep(x) legend star(* 0.10 ** 0.05 *** 0.01) title("xxxs\label{tab1}")  ///
            s(N mD controls districtfe yearfe provinceyearfe r2, labels("N" "DV Mean" "Controls" "District FE" "Year FE" "Province-Year FE" "R$^2$")) 

end
Here is the sample dataset

Code:
* Example generated by -dataex-.    To install: ssc install    dataex
clear
input float year double(district    x1) float x2
2017 10115    48576  10.79293
2016 10115    43770 10.815013
2015 10115  41768.5 10.758085
2014 10115    40440 10.835257
2013 10115  42452.5  10.84151
2012 10115  44574.5 10.911667
2011 10115    39676 11.004084
2010 10115    31842 10.959435
2009 10115    31312  10.89785
2008 10115    26465 10.878846
2007 10115    22618 10.935728
2006 10115    18904 10.812347
2005 10115  16661.5 10.809118
2004 10115  13500.5 10.735826
2003 10115  10517.5 10.508248
2002 10115    10627 10.447365
2001 10115   6838.5  9.866043
2000 10115     4900  9.621317
2017 10311    61813 11.096008
2016 10311  48625.5 11.079721
2015 10311  37815.5 10.957888
2014 10311    32250  11.23849
2013 10311    33426 10.378188
2012 10311    34349 10.438468
2011 10311  35095.5  10.45002
2010 10311  32806.5 10.079932
2009 10311    32279  9.947844
2008 10311  28781.5 10.185665
2007 10311    21234  9.931454
2006 10311  15583.5  9.760022
2005 10311  12846.5  9.747766
2004 10311    11463  9.614722
2003 10311   8987.5  9.846739
2002 10311   7776.5  9.959849
2001 10311     6775   9.99496
2000 10311   5757.5 10.296524
2017 10313 112668.5 11.144252
2016 10313  95427.5 10.954016
2015 10313    79615  11.08856
2014 10313  73342.5 10.964838
2013 10313  73856.5  10.60652
2012 10313  64961.5 10.615115
2011 10313    61735 10.558088
2010 10313  53093.5  10.42195
2009 10313    55702 10.306606
2008 10313    64201 10.483128
2007 10313  47188.5 10.229994
2006 10313    36686  9.971215
2005 10313    31178   9.89325
2004 10313  27739.5  9.813892
2003 10313  22792.5  9.709494
2002 10313    17761  9.577569
2001 10313  20133.5  9.581846
2000 10313    13951  9.311994
2017 10511  25332.5 10.485425
2016 10511  25148.5  10.67426
2015 10511  20135.5 10.293143
2014 10511  17865.5 10.303815
2013 10511    17418 10.039917
2012 10511    16789 10.041409
2011 10511    17177 10.004248
2010 10511  11455.5   9.51729
2009 10511     9417  9.434856
2008 10511     8410 9.3116665
2007 10511     4460   9.78344
2006 10511     3907  9.567475
2005 10511   3252.5  9.332502
2004 10511   2632.5  9.066351
2003 10511     1958  8.596397
2002 10511   1850.5  8.336612
2001 10511     1821  8.193471
2000 10511   1471.5  7.489792
2017 10515    10937   9.57191
2016 10515    10664  9.560899
2015 10515   9949.5  9.460496
2014 10515   8403.5  9.507476
2013 10515   8413.5   9.30918
2012 10515     8810   9.36443
2011 10515     9858  9.356923
2010 10515   6615.5  9.749888
2009 10515     5279 9.0668125
2008 10515   5224.5  9.306926
2007 10515     4465  9.582626
2006 10515   2990.5  9.108054
2005 10515     2520  8.847734
2004 10515   2080.5   8.88162
2003 10515     1688  9.225299
2002 10515   1454.5  8.700666
2001 10515   1180.5  8.328477
2000 10515     1054  8.524872
2017 10517    26045  9.695479
2016 10517    25148  9.818636
2015 10517  21828.5  9.608504
2014 10517  22442.5    9.5386
2013 10517    23993  9.438197
2012 10517    24766  9.768464
2011 10517    25376  9.609882
2010 10517  20834.5  9.421533
2009 10517    20022  9.211345
2008 10517  17199.5  9.941608
end

Thank you,
Marina