Assigning Values within a dynamically named matrix in R

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I am struggling with a loop in R where I have to use dynamic variable names (which I am told is a bad idea from the other posts about dynamic variable names, but I am pretty sure that I need to based on my file structure). Each folder for which the loop enters, there is a different number of files.

The dynamic variable names contain matrices and I need to look in each row/column of the matrix and output a new matrix.

Streamlined example: var 1 is a 40x40 matrix var 2 is a 45x45 matrix var 3 is a 40x40 matrix

for (f in 1:(length of var3s))  # the number of files in the folder, in each folder do: 

For (g in 1: ncol(var1)) {  
  For (h in 1: nrow(var1)) {
    if (var 1[g,h]>4 & var 2[g,h]<1)
          { var3[f] [g,h]<-1}    # <- you cannot do this, but this is ultimately what I want 
}
}

I want to take the f-th variable matrix from variable 3's list and assign a value to the location at [g,h] I've done this before with real variable names, but I am struggling with adding the dynamic element. This is what it looks like and the errors I'm getting.

for (f in 1:(length(LD139_040))){
  assign(paste0("LD139_040s",f),
  matrix(0,nrow(eval(parse(text=paste0("B139_040",f)))),
  ncol(eval(parse(text=paste0("B139_040",f)))))) # this effectively creates my new matrix (var3 above) the size I need based on the files above

for (g in 1:(ncol(eval(parse(text=paste0("B139_040",f)))))){
  for (h in 1:(nrow(eval(parse(text=paste0("B139_040",f)))))){
  if (S139_040[g,h]>10 & 
  (assign(paste0("LD139_040",f), as.matrix(raster(LD139_040[f]))))[g,h]>.295 & 
  (assign(paste0("LD139_040",f), as.matrix(raster(LD139_040[f]))))[g,h]<.33 &  
  (assign(paste0("B139_040",f), as.matrix(raster(Blue139_040[f]))))[g,h]<180) 
    # this section also works and will give me a t/f at each location [g,h]
    # if true, assign the value 1 to the new matrix LD139_040 at f
  {assign(paste0("LD139_040s", f)[g,h], 1)}

   }
  }
}

I have tried a variety of combinations of eval and assign to organize the last statement, and I get errors such as 'invalid first assignment', incorrect number of dimensions, and target of assignment expands to non-language object.

Thanks for your help!

R version 3.1.1 "Sock it to Me" with library(raster)

asked 38 secs ago

Jessica F

1

Assigning Values within a dynamically named matrix in R