Tabulation issues with "if" statements

[Wayde Flowerday]

Hi folks,

I am unsure of where to find this, and I have looked. Potentially I am trying to treat Stata too much like Matlab or Mathematica.

All I want to do is tabulate variables using many if statements.

i.e

Tab variableX if (weight>90kg in 2000) & (weight<90kg in 2005).

How would I do this?

Thanks in advance

[Svend Juul]

You must tell more about the structure of your data. For example, do you have one observation per person (wide format), or do you have one observation per person and year (long format)?

Other points: tab (not Tab) is an abbreviation of tabulate. If weight contains the weight in kg, it is ...weight>90..., not ...weight>90kg...

[Jorrit Gosens]

This depends a lot on how your data is organized. E.g., is weight in 2000 one variable, and weight in 2005 another, or do you have panel data with person ID, weight and moment of measurement?

[Wayde Flowerday]

Hi guys,

I was being silly. I reshaped my data into wide format and now I can do everything I need.
Rookie error on my part.

Thanks for the replies.

[Nick Cox]

It can be done with a long structure too. Presumably you have variables something like identifier, weight, year.

 
egen wanted = total((weight > 90 & year == 2005) | (weight < 90 & year == 2010)), by(id) 
tab <something> if wanted == 2

The conditions

 
weight > 90 & year == 2005 

weight < 90 & year == 2010

will be evaluated as 1 when true and 0 when false. You want persons for which both are true, so they will score a total of 2.

A key detail is that the conditions will not be (cannot be) true in the same observation with a long structure, so you need logical or, not logical and, even though you are looking for persons for whom both are true.

For more, see http://www.stata-journal.com/sjpdf.h...iclenum=dm0055