Buzz Burhans ruminated
>
> I would appreciate help with creating the following value,
> I can't seem to
> get it right:
>
> I have data with 4 vars in each record as follows:
>
> 1. farmID is an ID variable for farm
> 2. cowID is an ID variable for cow (within farmID)
> 3 enterPen is the date on which a cow enters Pen
> 4 exitPen is the date on which the cow exits Pen
>
> There are multiple cows within each farm, and their
> enterPen and exitPen
> dates vary individually.
>
> What I need is a variable that contains the count of cows
> within the same
> farmID which have entered, but not yet exited the Pen on the date an
> individual cow exits the Pen,
>
> i.e.a count of "other cows" within the same farmID whose
> enterPen date is
> < exitPen date for each individual cow (within the same
> farmID) and whose
> exitPen date (the "other cows" ) is > the exitPen date for
> the individual
> cow ...
>
> I can't seem to get the ifs to work correctly across
> different records,
> probably because I'm not very good at looping.
>
There may be a way to approach this with -st-
but -st- is not my daily bread, so I will
pass on that and try a direct approach.
I don't think -if- enters here, nor need
any looping. I surmise that you can get exactly
what you want with -by-. It's just that I
don't understand exactly what you want.
Any cow is still within the farm until the
day it exits. I don't see that -enterPen-
is relevant so long as -enterPen- <= -exitPen-.
A step towards what you want is, I think,
bysort farmID (exitpen) : gen enteredsofar = _n
qui by farmID exitpen :
replace enteredsofar = enteredsofar[_N]
The number of other cows appears to be central,
which means subtract 1 from this, I guess.
Nick
[email protected]
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