Hi Mac, The first entry is 0 for water balance. That means the 3rd should be zero according to the formula.
Water balance today = Water balance yesterday + Rainfall − Evaporation This loop gives 5 for each date. I don't see why ? May Rainfall Evaporation Water_Balance 1 7 0 5 0 2 8 10 5 NA 3 9 0 5 NA 4 10 0 5 NA 5 11 2 5 NA 6 12 23 5 NA Regards, Frederic. Frederic Ntirenganya Maseno University, African Maths Initiative, Kenya. Mobile:(+254)718492836 Email: fr...@aims.ac.za https://sites.google.com/a/aims.ac.za/fredo/ On Thu, Oct 23, 2014 at 7:17 PM, MacQueen, Don <macque...@llnl.gov> wrote: > If I understand the problem correctly, then I’d suggest this: > > ndays <- nrow(Wb30) > > for (iday in 2:ndays) { > > Wb30$Water_Balance[iday] <- Wb30$Water_Balance[iday-1] + > Wb30$Rainfall[iday] - Wb30$Evaporation[iday] > > Wb30$Water_Balance[iday] <- min(Wb30$Water_Balance[iday], 100) > Wb30$Water_Balance[iday] <- max(Wb30$Water_Balance[iday], 0) > > } > > It may be possible without a loop, but I think a loop is easier to > understand in the current circumstances. And is likely to be fast enough > that it does not matter. > > - > Don MacQueen > > Lawrence Livermore National Laboratory > 7000 East Ave., L-627 > Livermore, CA 94550 > 925-423-1062 > > > > > > On 10/23/14, 5:33 AM, "Frederic Ntirenganya" <ntfr...@gmail.com> wrote: > > >Dear All, > > > >I want to calculate water balance using the following formula: > >Water balance today = Water balance yesterday + Rainfall - Evaporation > > > >This is a sample of data I am using: > > > >head(Wb30) > > May Rainfall Evaporation Water_Balance > >1 7 0 5 0 > >2 8 10 5 NA > >3 9 0 5 NA > >4 10 0 5 NA > >5 11 2 5 NA > >6 12 23 5 NA > > > >The following is the loop am trying to use but it is not working well. > > > >#Water balance today = Water balance yesterday + Rainfall - Evaporation > >#If Water balance today < 0 then Water balance today = 0 > >#If Water balance today > 100 then Water balance today = 100 > >wb=c() > >for (w in 1:length(Wb30$Water_Balance)){ > > if(w<0 & w>100){w<-0 & w<-100} > > #print (w); > > for (i in 1:length(Wb30$Rainfall)){ > > for (j in 1:length(Wb30$Evaporation)){ > > } > > } > > wb<-Wb30$Water_Balance[w] + Wb30$Rainfall[i+1]-Wb30$Evaporation[j+1] > >} > >wb > > > >Any suggest of what I am missing for it to work correctly is welcome. > > > > > >Regards, > > > >Frederic Ntirenganya > >Maseno University, > >African Maths Initiative, > >Kenya. > >Mobile:(+254)718492836 > >Email: fr...@aims.ac.za > >https://sites.google.com/a/aims.ac.za/fredo/ > > > > [[alternative HTML version deleted]] > > > >______________________________________________ > >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. > > [[alternative HTML version deleted]] ______________________________________________ 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.
