Bookmark and Share

Notice: On March 31, it was announced that Statalist is moving from an email list to a forum. The old list will shut down on April 23, and its replacement, statalist.org is already up and running.


[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: st: Question on loop over variable


From   Andrew Dyck <tempmail@andrewdyck.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Question on loop over variable
Date   Thu, 28 Jul 2011 23:08:16 -0700

I'm going to suggest trying to avoid the foreach loop using -bysort-.

It looks like you are already using it for the variable _monthly_ to
create a price per itemid for every month (presumably your data is
daily or weekly?). I would suggest considering the following:

1. collapse your data to be monthly
collapse (sum) extendedcost itemqty, by(monthly)

2. generate a price variable
gen purchase price = extendedcost / itemqty

3. generate an average price by itemid
bysort itemid : egen average_purchase_price = mean(price)

Maybe I've misunderstood your aims but hopefully that is of some help

Cheers,
Andrew

On Thu, Jul 28, 2011 at 6:12 PM, Guo Chen <chenx711@umn.edu> wrote:
> Hi, all:
>
> I wanna calculate monthly average purchase price for all the products
> in my data set, so I need loop over all values of variable "itemid".
>
> I checked http://www.stata.com/support/faqs/data/foreach.html  and the
> following code is the best I can do, but I still got error messege:
>
>
> file C:\DOCUME~1\MPTMP026\LOCALS~1\Temp\ST_0000000t.tmp not found
> r(601);
>
> Can you please take a look at my code?
>
> ==========begin code=========
> use data, replace
>
> tempfile data
>
> levelsof itemid, local(levels)
>
> foreach l of local levels{
> use "`data'", clear
> keep if itemid == "`l'"
> bys monthly: replace total_purchase_price = sum(extendedcost)
> bys monthly: replace total_quantity = sum(itemqty)
> replace average_purchase_price = total_purchase_price / total_quantity
>
> bys monthly: gen i = [_n]== 1
> drop if i != 1
> outsheet using "C:\Documents and Settings\MPTMP026\Desktop\new\`l'.txt"
> }
>
>
>
> --
> Guo Chen
> University of Minnesota
> Dept. of Applied Economics
> 125-E Ruttan Hall
> 1994 Buford Avenue
> St. Paul, MN 55108
> 612-423-7031
> *
> *   For searches and help try:
> *   http://www.stata.com/help.cgi?search
> *   http://www.stata.com/support/statalist/faq
> *   http://www.ats.ucla.edu/stat/stata/
>

*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/


© Copyright 1996–2014 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   Site index