using foreach to generate mean values of variables

[Dai Grove-White]

I have a dataset of microbial counts with each variable being a count of that organism in a faecal sample from a pony identified by variable ponyid. Samples were taken serially on a daily basis for 15 days thus each row represents a sample identified by the variable sampleno which has a value of 1-15. For each microbe - I wish to get the mean of the count from the last 3 days. I have used the following code for a given microbe -"fibrobacter"

bysort ponyid (sampleno):gen avNfibro= (fibrobacter[_N] + fibrobacter[_N-1] + fibrobacter[_N-2])/3

this works for the specific variable 'fibrobacter' and produces a column containing one number per pony which is the mean of the last 3 counts

I wish to use foreach to produce the same variable for each microbe (there are about 100)
I have tried

foreach var of varlist fibrobacter- pluralibacter {
bysort ponyid (sampleno): gen avN`var' = 'var'[_N] +'var' [_N-1] +'var' [_N-3])

}
this gives an error message 'var' invalid name (r198)

I have also tried
foreach var of varlist fibrobacter- pluralibacter {
bysort ponyid (sampleno): gen avN`var' = (sum([_N] + [_N-1] + [_N-3]))/

}
this runs but gives a variable which is numericallly incorrect

Help would be gratefully accepted

Thank you

Dai Grove-White,
University of Liverpool

[Carlo Lazzaro]

Dai:
try your code copying and pasting in it:

`var'

when necessary.

[Nick Cox]

Your first line of code has the right spirit but the others introduce errors of various kinds.

sort ponyid sampleno

foreach v of varlist  fibrobacter-pluralibacter {

    by ponyid:  gen avN`v'= (`v'[_N] + `v'[_N-1] + `v'[_N-2])/3

}

[Dai Grove-White]

It works! Thanks, Nick
Dai