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]]
>
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