Simple loop (parallel with two lists of numbers)

[josh scott]

Hi All,

I am new to loops, especially running them in parallel fashion. I want to change years in data files as well as number sets from files. I have no idea if I am doing this correctly.

Here is my code example.

local LIST 41 49 50 52 53 54 55 56 57 58 59 60

set trace on

forval i=0/4{
foreach in local LIST {
clear
cd "C:\Users\jsco131\Documents\extracts\RMS\201`i ’"

import delimited C:\Users\jsco131\Documents\extracts\RMS\201`i’\Mov ement_Files\5003_201`i’\50`LIST’_201`i’.tsv

merge m:1 store_code_uc using "C:\Users\jsco131\Documents\extracts\RMS\201`i’\st ores_201`i’.dta"

keep if _merge==3
drop _merge
save StoreData50`LIST’_201`i’.dta

}

}

set trace off



How do I fix this?

Thank you in adavance.

-Josh

[George Ford]

tricky to really see what's up, but try this.

You need a indicator for the foreach loop. I've used s.
There were some spaces in some words, but that may be a copy/paste issues.
Why "tsv" rather than "csv" ?
I prefer -joinby- to merge m:1. It will only keep the matches as written and do the m:1 match (I think).

local LIST 41 49 50 52 53 54 55 56 57 58 59 60
forval  i =0/4 {
     foreach s in local LIST {
     clear
     di "Outer loop = " `i'
     di "Inner loop = " `s'
     cd "C:\Users\jsco131\Documents\extracts\RMS\201`i ’"
     import delimited C:\Users\jsco131\Documents\extracts\RMS\201`i’\Movement_Files\5003_201`i’\50`s’_201`i’.csv 
     joinby store_code_uc using "C:\Users\jsco131\Documents\extracts\RMS\201`i’\stores_201`i’.dta" 
     drop _merge
     save StoreData50`s’_201`i’.dta
     }
}

[Nick Cox]

First off, you have nested loops. not loops in parallel. As far as I can see the original code will fail as

foreach in local LIST

should be more like

foreach s of local LIST

There were two errors there and George Ford 's helpful rewriting corrected one.

The line

 cd "C:\Users\jsco131\Documents\extracts\RMS\201`i ’"

could usefully be moved up out of the inner loop, as you need to cd 5 times (but not 60 times).

[Clyde Schechter]

Why "tsv" rather than "csv" ?

Some people use .txv as a filename extension for text files with tab-separated variables.

[josh scott]

Thank you all for your input!

I tried writing the nested loops in George Ford 's style and change the inner loop to "foreach s of local LIST", but it currently won't change the directory, which I have never had a problem with. It also didn't matter whether I had it inside both loops or not.

Any reason why this is occurring?

[George Ford]

before and after the cd command type pwd and see what happens. It will display the active directory.

or just delete the cd line and add the directly to the save line (if that is why you cd in the first place).