Michael Hills <[email protected]> wrote:
> I was disturrbed to find that in the latest ado update the cut
> function of egen has changed how it deals with missing values.
>
> In the version before the update, when you cut a variable with missing
> values, these were coded as missing in the new variable. Now they are
> coded with the upper limit specified in cut.
>
> I can see no logic in this and I presume it is an error which has been
> introduced during the latest update of cut. There is no change in the
> help file for egen.
The change to -egen, cut- was intentional; it was pointed out by a
user that its behavior did not match the documentation. I concurred
and modified the function to better match the documentation.
Previously when -egen, cut- was used with the -at- option, the
(ascending) list of numbers are intended left hand endpoints for
subdividing the data. However any member of the input data greater
than or equal to the largest value in -at- got mapped to missing.
This contradicted the notion that the list of numbers was intended
as left hand endpoints.
I modified -egen, cut- so that the values of the input data that are
greater than or equal to the largest value in -at- are mapped to the
largest value in the -at- list.
Since missing values are greater than numerical values, this resulted
in the behavior that now missing values are mapped to the largest
value specified in -at-. This makes sense to me given that the values
in -at- are intended as left hand endpoints.
If the user wishes to exclude missing values, it is easy to accomplish
this using the -if- or -in- options. For example,
. egen newx = cut(x), at(2, 4, 6) if x != .
The documentation for -egen, cut- says nothing about what happens
to missing values, but perhaps it should. I'll get that done.
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--Jean Marie
[email protected]
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