CUMUL command

[Zeev Maoz]

I am using the cumul command to generate cumulative values for observations. For example,
cumul x, g(y) by (a).

However, I am getting different y values for the same values of x within stratum a.
Not sure why this is happening. Any suggestions?
Zeev

[Nick Cox]

See documentation for an equal option and comments within https://www.stata.com/support/faqs/s...ing-positions/

The calculation of the empirical cumulative distribution, at least as implemented in Stata, is a related but subtly different problem. In official Stata, this calculation may be performed using cumul. cumul by default appears to be most closely geared to preparing a plot of cumulative probabilities (y axis) versus observed values (x axis). When tied values occur, cumul will not (again, by default) assign the same cumulative probability to each tied value. This is immaterial and indeed even desirable for graphical purposes: vertical line segments will be produced whatever the convention about ties, and when visible plot symbols are used, it is often helpful to get an impression of the frequency of ties. In contrast, this FAQ is focused mainly on problems in which identical values should all be assigned the same proportion or percentage. Incidentally, an equal option was added to cumul on 17 June 2003 to override the default and ensure that this condition is satisfied.

[Zeev Maoz]

Thanks. I figured this out, but wasn't sure why this is happening.
Zeev