st: Datamanagement: warning when using infile with optional if

[<A.T.Wolters@lse.ac.uk>]

Dear all,

I am reading ASCII data with a dictionary using the command -infile-
whilst conditioning on an variable (using -if-) that is read in the same
time. I created a simplified example to show you what is happening:

The data looks like:
-----------------data.txt--------------
1Ajohn1
1B8724
2Ajane0
2B8625
3Amark1
-----------------------------------------

With dictionary file
-----------------dctB.dct--------------
dictionary using data.txt {
 _column(1)	int	id	%1f	"Identifier"
 _column(2)	str1	cat	%1s	"Category"
 _column(3)	int	dob	%2f	"Date of Birth"
 _column(5)	int	age	%2f	"Age"
 }
-----------------------------------------

My aim is to read only those lines where the variable cat is equal to B.
I do this by making use of the command
infile using dctB if cat=="B"

I do end up with the required result. Stata does a great job at
conditioning on a variable that it is reading at the same time, however,
it returns an error for every line where cat=="A" as it contains non
numeric characters, where Stata expects only integers. Not only does
this produce messy .log files (especially with thousands of lines), it
indicates that Stata has to read every line completely which is time
consuming and somewhat unnecessary. 

Does anyone have a suggestion to improve on my current method?
Preferably one that produces readable .log files?

Thanks for your consideration,

Arne Wolters
London School of Economics

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