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: fredo at aims.ac.za
https://sites.google.com/a/aims.ac.za/fredo/
[[alternative HTML version deleted]]
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: fredo at aims.ac.za > https://sites.google.com/a/aims.ac.za/fredo/ > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help at 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. >
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" <ntfredo at
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: fredo at aims.ac.za
>https://sites.google.com/a/aims.ac.za/fredo/
>
> [[alternative HTML version deleted]]
>
>______________________________________________
>R-help at 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.