R help - Jul 2012 - remove loop which compares row i to row i-1

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.

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

	[[alternative HTML version deleted]]