Of course it _should_ be:

ifelse(x[-length(x)] < x[-1], ...,...)

Sorry...

-- Bert


On Tue, Jul 3, 2012 at 1:00 PM, Bert Gunter <bgunter@gene.com> wrote:

> Vectorize vectorize vectorize!
>
> if(x[-length(x)] < x[-1]) {...}
>
> (where x is the whole vector of entries)
>
> Bill Dunlap has posted some elegant code within the last month or 2 aimed
> at this sort of thing, so search on his posts in the archive.
>
> -- Bert
>
> On Tue, Jul 3, 2012 at 12:10 PM, jcrosbie <james@crosb.ie> wrote:
>
>>
>> I would like to remove a loop to speed up my code.
>>
>> I want to remove a loop which references the last row.
>>
>> In general I want to a remove a loop which looks something like this:
>> for 2 to number of rows in a matrix do{
>> if indextrow-1 is < currentIndexRow then do something.
>> }
>>
>>
>> My R code:
>>
>>     for (i in 2:length(tUnitsort$Hour)){
>>       ifelse(tUnitsort[i,4]>=tUnitsort[i-1,4],(tempMC
>> =tUnitsort[i,7]),tempMC ) #col. 4 = BlockNumber; note tests to see if the
>> offers have change to the next set of blocks.
>>       ifelse(tUnitsort[i,4]>=tUnitsort[i-1,4],(tempAC
>> =tUnitsort[i,7]-(tUnitsort[i,8]-tUnitsort[i,9])),tempAC )
>>       tUnitsort$MC[i] <- tempMC
>>       tUnitsort$AC[i] <- tempAC
>>       tUnitsort$PercentofMC[i] <- tUnitsort$Size[i]/tempMC
>>       tUnitsort$PercentofAC[i] <- tUnitsort$AvailableMW[i]/tempAC
>>     }
>>
>> --
>> View this message in context:
>> http://r.789695.n4.nabble.com/remove-loop-which-compares-row-i-to-row-i-1-tp4635327.html
>> Sent from the R help mailing list archive at Nabble.com.
>>
>> ______________________________________________
>> R-help@r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
>
>
> --
>
> Bert Gunter
> Genentech Nonclinical Biostatistics
>
> Internal Contact Info:
> Phone: 467-7374
> Website:
>
> http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm
>
>
>


-- 

Bert Gunter
Genentech Nonclinical Biostatistics

Internal Contact Info:
Phone: 467-7374
Website:
http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm

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