[R] Sum of two consecutive number in dataset.

[Tom Wright]

A couple of observations:
1) I'm not sure what the variable i is doing, looks like you are trying
to loop through years but perhaps you left that bit of code out for
clarity.
2) On the first loop of i you are assigning the values of
Samaru56[sow_day,] to all values in Samaru56. For future loops all
values on Samaru56 will be the same.

My approach to this problem would be:
rowCount<-nrow(Samaru56)
Samaru56$two_day<-vector(length=rowCount)

#first day doesnt have a two day value
Samaru56$two_day[2:rowCount]<-
	Samaru56$Rain[1:rowCount-1] + Samaru56$Rain[2:rowCount]

sow_day <- min(c(
		which(Samaru56$Rain > 20 & Samaru$Day>91),
		which(Samaru56$two_day > 20 & Samaru$Day>91)))


#first day doesnt have a two day value

On Wed, 2014-10-15 at 10:01 +0300, Frederic Ntirenganya wrote:
> Dear All,
> 
> i am solving the following problem in my work.
> 
> The first day from April 01 that gets more than 20 mm on a single day, or
> totalled
> over 2 consecutive days. i.e April 01 = 92th day of the year.
> 
> The column of interest is "Rain".
> > head(Samaru56)
>   Year Day Rain
> 1 1928   1    0
> 2 1928   2    0
> 3 1928   3    0
> 4 1928   4    0
> 5 1928   5    0
> 6 1928   6    0
> 
> I used the loop below but it is not printing anything.
> 
> sow_day=c()
> for (i in 1928:1983){
>   for (j in 92:366){
>     k=j-1
>     s_rain=Samaru56$Rain[k] + Samaru56$Rain[j]
>     if (s_rain>=20)
>       sow_day=j
>       break
>   }
>   Samaru56$year=Samaru56$Year[sow_day]
>   Samaru56$Day=Samaru56$Day[sow_day]
>   Samaru56$Rain=Samaru56$Rain[sow_day]
> }
> sow_day
> 
> Any idea is welcome on how I can solve this problem. Thanks
>