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From |
Nick Cox <n.j.cox@durham.ac.uk> |

To |
"'statalist@hsphsun2.harvard.edu'" <statalist@hsphsun2.harvard.edu> |

Subject |
st: RE: looping panel data |

Date |
Tue, 4 Oct 2011 12:06:31 +0100 |

You are a bit confused about -foreach- syntax, but that is secondary. (I think you meant to use `store' within the loop, not `store_number'.) However, I don't see a need for any loops here. This should be one line of Stata. The basic trick is egen P_nt = total(expression), by(store week) Your expression is exp_share9401000* avgp9401000+ exp_share9401870* avgp9401000+ exp_share9402500* avgp9402500+ exp_share9402600* avgp9402600+ exp_share9405400* avgp9405400+ exp_share9408160* avgp9408160+ exp_share9410100* avgp9410100+ exp_share9410200* avgp9410200+ exp_share9450850* avgp9450850+ exp_share9451200* avgp9451200+ exp_share9451000* avgp9451000 except that it looks as if there is a typo there and it should be exp_share9401000* avgp9401000+ exp_share9401870* avgp9401870+ exp_share9402500* avgp9402500+ exp_share9402600* avgp9402600+ exp_share9405400* avgp9405400+ exp_share9408160* avgp9408160+ exp_share9410100* avgp9410100+ exp_share9410200* avgp9410200+ exp_share9450850* avgp9450850+ exp_share9451200* avgp9451200+ exp_share9451000* avgp9451000 Nick n.j.cox@durham.ac.uk Tomáš Houška I would like to ask you for a help with my looping problem. I have sales panel data with variables week ID, store ID, product ID, price, expenditure_share (share of expenditures for a given product across all products in dataset) I would like to compute Stone price index defined as P_nt=SUM (expenditure_share_int * P_int ). This means that for each combination of store (n) and week (t) I need to compute a multiple of expenditure_share and price for each product (i) and then sum it up over all products sold in the particular store that week. The result is again a panel data variable P_nt which is a price index for each week and store. It is an expenditure system index, so the more you spend on more expensive products (keeping prices constant), the higher the index. And I cannot figure out a way how to calculate P_nt index. I have come up with a loop, which saves the results in a new dataset, but it is not working. I would be very glad for any help on how to calculate this variable. Here is my looping command (j=week number, store_number is a local macro with list of store numbers - they are from 2-131 but with missing values (i.e. not consecutive)) postfile index_file store week index using stone_index_res, replace foreach store in `store_number' { forvalues j=91/317 { gen index`store_number'`j' = exp_share9401000* avgp9401000+ exp_share9401870* avgp9401000+ exp_share9402500* avgp9402500+ exp_share9402600* avgp9402600+ exp_share9405400* avgp9405400+ exp_share9408160* avgp9408160+ exp_share9410100* avgp9410100+ exp_share9410200* avgp9410200+ exp_share9450850* avgp9450850+ exp_share9451200* avgp9451200+ exp_share9451000* avgp9451000 if week==`j' & store==`store_number' post index_file (`week') (`store') (index`store_number'`j') } } postclose index_file * * 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/

**Follow-Ups**:**Re: st: RE: looping panel data***From:*Tomáš Houška <xbender@gmail.com>

**References**:**st: looping panel data***From:*Tomáš Houška <xbender@gmail.com>

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