st: tokenize and missing

[Ronnie Babigumira <rb.glists@gmail.com>]

Hello,

I have a quarterly data set and I am trying to identify missing cases

houscode       qtr   wage_ld  biz_lead
      72         1         0         0
      81         1         0         1
      81         2         .         1
      11         3         0         1
      10         4         .         .
       9         1         1         0

I started by using Nick Cox's very useful -nmissing- (ssc install nmissing)

Which gave me

wage_ld             2
biz_lead            1


Knowing which variables have missing cases, I

list if mi(wage_ld, biz_lead)

However, to generalize it (I will be doing it by quarter) I used

nmissing
tokenize `r(varlist)'
list if mi(`1' `2')

This works for the data as it is, however, you will notice that the missing cases are in qtr2. So, if I did this 
analysis by quarter and I

keep if qtr == 1
nmissing
tokenize `r(varlist)'
list if mi(`1', `2')

I get ........invalid syntax...............

I reckon this is coming from the fact that indeed for qtr == 1, I do not have two variables with missing data. So, is 
there a way I can tweak this to allow it to proceed?

Ronnie
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