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Re: st: FW: How to make 'contract' create a row of zerofrequencies?

From   Roger Harbord <>
Subject   Re: st: FW: How to make 'contract' create a row of zerofrequencies?
Date   Mon, 22 May 2006 13:24:01 +0100

One solution could be to use -tabcount- by Nick Cox, available from SSC. You specify a list of values which define the categories of a variable that are to be counted, and zero frequencies are then included. The -replace- option makes it function much like -contract-, except zero frequencies are retained for the specified values.


--On 22 May 2006 11:52 +0100 Pauline Rogers <> wrote:

Dear All,

I have a large dataset containing information on individuals attending for
screening at several centres.

I am writing a program to summarise monthly attendance, to be run
regularly by one of our administrators.  So I first 'contract' my data to
create a new dataset of the number of attendances for each centre for
each month.  I used the following statement:

contract centre3 mrec, freq(count) zero

(Centre3 = centre code, mrec = month code)

I have discovered that when there are no attendances in a month at any of
the centres, Stata completely excludes this month rather than create a
zero count for each centre.

This then completely throws out my summary statistics.  Is there any way I
can force 'contract' to create a count of zero for each centre for any
month with zero attendance at all centres?
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