Dear Duncan, Those condition should be there and also look at Rainfall and evaporation columns. If i change it to be like the following loop, it can't do it.
The problem is how to include those conditions and also respect the formula? wb=c() for (w in 1:length(Wb30$Water_Balance)){ if(w<0){ w=0 } wb=Wb30$Water_Balance[w-1] + Wb30$Rainfall[w]-Wb30$Evaporation[w] } wb 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 3:44 PM, Duncan Murdoch <murdoch.dun...@gmail.com> wrote: > On 23/10/2014, 8:33 AM, Frederic Ntirenganya 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$Water_Balance)){ > > if(w<0 & w>100){w<-0 & w<-100} > > The line above doesn't make sense. It is impossible for w to be both > less than 0 and greater than 100, so the condition will never be true. > And if it is true, "w<-0 & w<-100" is not a sensible thing to do. > > > #print (w); > > for (i in 1:length(Wb30$Rainfall)){ > > for (j in 1:length(Wb30$Evaporation)){ > > } > > } > > Those loops do nothing. > > > wb<-Wb30$Water_Balance[w] + Wb30$Rainfall[i+1]-Wb30$Evaporation[j+1] > > Those should be using w-1 in place of w, and w in place of i+1 and j+1. > > Duncan Murdoch > > > } > > 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.