I am trying to find the value of k which is a constant in Decompostion models
Wt = W0 e^-kt
I am using R script to calculate it. However, I am having trouble in selection of the data set.
Example data
Site Treatment Month Repli WD
W2 0 0 2 1
W3 0 0 1 .9
W7 0 0 3 .7
W12 0 0 4 .7
W2 0 1 2 .4
W3 0 1 1 .3
W7 0 1 3 .3
W12 0 1 4 .2
W2 0 3 2 .2
W3 0 3 1 .1
W7 0 3 3 .1
W12 0 3 4 .1
W2 0 4 2 .9
W3 0 4 1 .9
W7 0 4 3 .8
W12 0 4 4 .8
k=numeric(max(Cs$Repli))
pred=array(0,dim=c(4,max(Cs$Repli)))
resid=array(0,dim=c(4,max(Cs$Repli)))
obs=array(0,dim=c(4,max(Cs$Repli)))
Now the part I am having a problem Nonlinear reggression
for(i in 1:max(Cs$Repli)){
s1=subset(Cs,Cs$Repli==i)
In my original data it selects only four data set like this (which is fine) May be because of having max Repli value?
Site Treatment Month Repli
W12 0 0 4
W12 0 1 4
W12 0 3 4
W12 0 5 4
Then I run the below command then I get the value of K for these 4 data. Now I want to select W2 or any other. How can I do that? I tried different things but I couldnt get the results. I tried using %in% but (i) from above script is also being used below so I cant use %in%. Any help would be really appreciated.
Month=s1$Month
WD=s1$WD
nonlin = nls(WD ~ 1*exp(-k*Month), trace=TRUE, start = list(k = .01))
summary(nonlin)
pr=predict(nonlin)
res=residuals(nonlin)
k[i]=coef(nonlin)[1]
pred[,i]=pr
resid[,i]=res
obs[,i]=WD
} #end of nls for loop
I can provide original data.
If you want to check which subsets you have processed, you may use an additionally variable W_subsets to store processed subsets:
# before the nls loop
W_subsets <- rep(list(NA), max(Cs$Repli))
# inside the nls loop
W_subsets[[i]] <- s1
As I may see, the output of W_subsets is all right:
[[1]]
Site Treatment Month Repli WD
2 W3 0 0 1 0.9
6 W3 0 1 1 0.3
10 W3 0 3 1 0.1
14 W3 0 4 1 0.9
[[2]]
Site Treatment Month Repli WD
1 W2 0 0 2 1.0
5 W2 0 1 2 0.4
9 W2 0 3 2 0.2
13 W2 0 4 2 0.9
... etc. to W12