Looping dataset R - r

Question

I'm trying to make a loop to automate a lot of actions in R. The code I have looks like this:
datA <- droplevels(datSUM[datSUM$Conc=="a",])
datB <- droplevels(datSUM[datSUM$Conc=="b",])
datC <- droplevels(datSUM[datSUM$Conc=="c",])
datD <- droplevels(datSUM[datSUM$Conc=="d",])
datE <- droplevels(datSUM[datSUM$Conc=="e",])
datX <- droplevels(datSUM[datSUM$Conc=="x",])
datY <- droplevels(datSUM[datSUM$Conc=="y",])
datAf <- droplevels(datA[datA$Sex=="f",])
datAf1 <- droplevels(datAf[datAf$rep=="1",])
datAf2 <- droplevels(datAf[datAf$rep=="2",])
datAf3 <- droplevels(datAf[datAf$rep=="3",])
datAm <- droplevels(datA[datA$Sex=="m",])
datAm1 <- droplevels(datAm[datAm$rep=="1",])
datAm2 <- droplevels(datAm[datAm$rep=="2",])
datAm3 <- droplevels(datAm[datAm$rep=="3",])
So since I have to do this 7 times, it seems like making a loop for this operation is the best way to do it. Can someone help me make that? I'm new to R so please bear that in mind.

Answer 1

Well I will have a stab at this.
concs <- c(a='a',b='b',c='c',d='d',e='e',x='x',y='y')
sex <- c(m='m',f='f')
reps <- c(rep1='1',rep2='2',rep3='3')
# By using m='m' we can label the objects within the list, making it
# easier to navigate the final object, otherwise use:
# concs <- c('a','b','c','d','e','x','y')
# sex <- c('m','f')
# reps <- c('1','2','3')
dfs <- lapply(concs, function(x){
droplevels(datSUM[datSUM$Conc==x,])}
)
sdfs <- lapply(sex, function(x){
lapply(dfs, function(y){
droplevels(y[y$Sex==x,])}
)}
)
rsdfs <- lapply(reps, function(x){
lapply(sdfs, function(y){
lapply(y, function(z){
droplevels(z[z$rep==x,])}
)}
)}
)
There is probably a better way to do this, that may involve using more lapplys but I think this "should" do the trick.
The only downside to this method you will have to access certain objects with rsdfs[[1]][[1]][[1]] or rsdfs[['rep1']][['m']][['a']] e.t.c
And applying functions to these would in itself require a bunch of lapplys
Let me know if this helps.
This is one method to do so - I will work on a more elegant solution later.