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For loop

3 messages · Ahmed Attia, Rui Barradas, Nordlund, Dan (DSHS/RDA)

Ahmed Attia
# 
Hello R users,

The code below is for loop in R that I want to do to following
calculation at each time i and i-1 in 2:75 dataset
(Litterfall_Ahmed97).


ac = ((LeafBiog at date i
-LeafBiog at date i-1, dataset = leafbiom97) + (littperiod at date i,
dataset= Litterfall_Ahmed97))/(sum (GPP from date i-1 to date i,
dataset=GPP_Ahmed13)/2) .

#code for loop

GPP_Ahmed13$Date <- as.Date(GPP_Ahmed13$Date, '%Y/%m/%d')
Litterfall_Ahmed97$Date <- as.Date(Litterfall_Ahmed97$Date, '%Y/%m/%d')
leafbiom97$Date <- as.Date( leafbiom97$Date, '%Y/%m/%d')
for (i in 2:75){
  (leafbiom97$LeafBiog[leafbiom97$Date == "i"] -
     leafbiom97$LeafBiog[leafbiom97$Date == "i-1"]+
     Litterfall_Ahmed97$littperiod[Litterfall_Ahmed97$Date =="i"])/
    (sum(GPP_Ahmed13$GPP[GPP_Ahmed13$Date >= "i-1" &
                           GPP_Ahmed13$Date <= "i"])/2)
}


#Error in charToDate(x) :

Thanks for your help


Ahmed Attia, Ph.D.
Agronomist & Soil Scientist
Rui Barradas
# 
Hello,

Without correcting your code, it's obvious that the expressions like 
leafbiom97$Date == "i" and all others with"i" and "i - 1" are wrong.
leafbiom97$Date is of class Date, not character. And, besides,
for(i in ...) makes of i a numeric variable that has nothing to do with 
"i". This "i" will remain the character string "i" for all iterations of 
the loop.

Hope this helps,

Rui Barradas

Em 22-06-2017 17:50, Ahmed Attia escreveu:
Nordlund, Dan (DSHS/RDA)
# 
For a reproducible example, you need to give us some example data, at least

dput(head(leafbiom97))
dput(head(Litterfall_Ahmed97))
dput(head(GPP_Ahmed13))


Dan

Daniel Nordlund, PhD
Research and Data Analysis Division
Services & Enterprise Support Administration
Washington State Department of Social and Health Services