Creating pointer for specific point in a dataframe - r

Question

A little background on the project before I get to the details. I'm working with a list of ~50 countries with data for somewhere between 40 and 60 years per country. I've been able to set up a loop for an individual country which tries out various values of a variable (named DELTA in the code) and logs results.
I first bring in the data and clean it to have no null values and create a vector containing all the 3 letter codes used to represent each country using the following code.
Clean <- na.omit(Data)
Clean <- Clean[order(country.isocode),]
Codes <- levels(Clean[,2])
I then use a loop and the subset function to create a different data frame for each country.
for (i in 1:length(Codes)) {
assign((Codes[i]),droplevels(subset(Clean,country.isocode==Codes[i])))
}
Now all 50 of my countries are in their own dataframe named after their 3 letter ISO code. The following is a the code I run to create the results I want for Angola (AGO).
AGO_Results <- matrix(numeric(0), 100,2)
AGOROW<-nrow(AGO)
for (j in 1:100) {
AGO[1,12]<-AGO[1,9]/DELTA
for (i in 2:AGOROW) {
AGO[i,12] <- AGO[i-1,12]*(1-DELTA)+AGO[i,9]
}
AGO[,13] <- AGO[,12]/AGO[,8]
AGO_Results[j,1] <- DELTA
AGO_Results[j,2] <- sum(AGO[,13] > 1 & AGO[,13] < 3)
DELTA=DELTA+.002
}
At the end of this AGO_Results contains the values I want, but I'd rather not do this manually for 50 countries, so I'm trying to create a loop around this for all 50 countries. I've managed using eval() and assign() to get rather far, but I'm stuck on what I think is the last hurdle.
for (k in 1:length(Codes)) {
# Initialize Delta and Create Storage Matrix and Row Count
DELTA <- .01
assign(paste(Codes[k],"_Results", sep=""), matrix(numeric(0), 100,2))
assign(paste(Codes[k],"ROW",sep=""), nrow(eval(as.name(Codes[k]))))
This portion is complete and works. Now we're at my real problem, how to reference the individual point [1,12] to be written in each data frame. What can I do to create a pointer to let me replace an individual item in a data frame, when I have to paste the name of the data frame in each time?
EDIT: Sample Data Posted below
country country.isocode year POP rgdpl ki rgdpl2wok rgdp investment workers L.P
21 Angola AGO 1970 5605.63 2366.51 23.27 5904.14 13265745651 3087431388 2246856 0.4
22 Angola AGO 1971 5752.96 2445.13 23.25 6127.95 14066747655 3270057880 2295508 0.4

Answer 1

First, there is a problem with
Clean <- Clean[order(country.isocode),]
(It will use a global variable country.isocode, not one in the data frame, if there is one. )
Instead of
for (i in 1:length(Codes)) {
assign((Codes[i]),droplevels(subset(Clean,country.isocode==Codes[i])))
}
you could do
xyz <- split(Clean, list(country.isocode)) # or, probably Clean$country.isocode
Now you have split the data frame by countries. You can lapply a function (possibly self-made) to the resulting list (xyz) and you get the results separately for each country. Try this and then say if you really need a "pointer".
edit after comments
xyz <- split(Clean, list(Clean$country.isocode))
xyz <- lapply(xyz, droplevels) # whatever that's for
Now you can define what you want to do with each country (I rewrote your code without trying to understand what it does but noted only an obvious problem):
doit <- function(x){
# where does the DELTA come from? do you initialize it to zero?
# anyway, you need to define it here or pass it as argument
Results <- matrix(numeric(0), 100,2) # I'd use 0 or NA instead of numeric(0)
NROWs<-nrow(x)
for (j in 1:100) {
x[1,12]<-x[1,9]/DELTA
for (i in 2:NROWs) {
x[i,12] <- x[i-1,12]*(1-DELTA)+x[i,9]
}
x[,13] <- x[,12]/x[,8]
Results[j,1] <- DELTA
Results[j,2] <- sum(x[,13] > 1 & x[,13] < 3)
DELTA=DELTA+.002
}
Results # returns results
}
And now you can apply the newly defined function to your list:
lapply(xyz, doit)
And that should be it. You probably need a few modifications and trials-and-errors but that's in my view a more sensible approach than creating lots of variables with assign.