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RE: st: egen anycount
Nick Cox <email@example.com>
RE: st: egen anycount
Tue, 24 May 2011 20:08:01 +0100
No; why would I suggest -reshape-? Your problems with looking for equality with fractions will bite regardless of long or wide form. It's soluble: as said, you use -float()- with floats and not with doubles.
The reality is much less picture perfect: a MET value is assigned from
a published compendium of physical activities. This compendium has a
single decimal point of precision (just like the last page on the
Wikipedia article). Of course, if I had a choice I would do the
calculations myself, thus preserving more accuracy, but I have to rely
on published sources and work within its constraints.
I suspect you are going to suggest using reshape... :-)
On Tue, 24 May 2011 18:20:46 +0100, Nick Cox <firstname.lastname@example.org>
> The problem can thus be traced upstream. Don't reduce such a variable
> to 1.2, 0.8, 1.5; if you really need such a variable map to integers
> with value labels.
> Thomas Speidel
> Nick, these values represent metabolic equivalent (MET) which is a
> measure of energy consumption.
> In this context I need to separate sedentary activities (</=1.5MET)
> from non-sedentary activities (>1.5MET)
> On Thu, 19 May 2011 13:21:48 +0100, Nick Cox <email@example.com>
>> I would advise circumspection here.
>> First off, wanting to know if something is equal to one of 1.2, 0.8,
>> 1.5 sounds an unusual kind of problem and it would be interesting to
>> know the context. For example, if these are codes in some
>> classification system, you might be better off holding the variable
>> string or mapped to integers with value labels.
>> Second, Daniel's hack solves one problem only to create another. The
>> code looks OK for -float- variables but for -double- variables it
>> often give the wrong answer. This can be seen directly with the
>> examples given:
>> . di 1.2 == float(1.2)
>> . di 0.8 == float(0.8)
>> . di 1.5 == float(1.5)
>> 1.5 _can_ be held as an exact binary in both -float- and -double-,
>> but most decimals can't. So, Daniel's program wouldn't catch 1.2 or
>> 0.8 in a -double- variable.
>> The bug is fixable and would require a branch in which a call
>> -float()- was not used if the variable was -double-.
>> On the whole, comparisons with decimals are best avoided, so seeking
>> work-arounds is, in my view, not a good strategy. For every program
>> like _ganycount where the file is short and a user-programmer is
>> willing to show you how to change it, there are many more where the
>> opposite is true.
>> daniel klein
>> I am not aware of a command, but it should not be hard changing the
>> existing -anycount-. Here's an ad hoc step-by-step
>> 1. locate -anycount- and open it in the do-file editor
>> . findfile _ganycount.ado
>> . doedit "`r(fn)'"
>> 2. change the file (don't save the changes yet)
>> 2.1 change line 2 form
>> "program define _ganycount"
>> "program define _ganycount2"
>> 2.2 change line 7 from
>> "[...] , Values(numlist int) /*"
>> "[...] ,Values(numlist) /*"
>> 2.3 change line 26 from
>> "*/ if ``i'' == `nj' & `touse'"
>> */ if ``i'' == float(`nj') & `touse'
>> 3. save the file as _ganycount2.ado to your "personal" folder
>> (to locate type: -di c(sysdir_personal)-) or alternatively to your
>> "plus/_/" folder (locate: -di c(sysdir_personal)-)
>> 4. -discard- Stata
>> 5. use your -anycount2- function
>> . egen somevar = anycount2(varlist), values(1.2 0.8 1.5)
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