R: for loop for subsetting data frame, conserving always first column

Question

i've a data frame with 253 columns, and 100000 + rows.

I want to make a subset of 2 columns, always keeping the first one, and summing 1 to take the next column from the right.

First loop: df[,c(1,2)]
Second loop: df[,c(1,3)]
....
Last loop: df[,c(1,253)]

I 've this code:

for(i in 2:length(colnames(df))){
    paste("a",i,sep ="") <- df[,c(1,i)]
    i += 1
}

But get this error:

> for(i in 2:length(colnames(df))){
+     paste("a",i,sep ="") <- df[,c(1,i)]
+     i += 1
Error: unexpected '=' in:
"    paste("a",i,sep ="") <- df[,c(1,i)]
    i +="
> }
Error: unexpected '}' in "}"

Note: I'm calling the new data frames a2, a3, ... Actually, i would like to name them, with the name of the corresponding colum. For example, TVs <- df[,c(1,2)] instead of: a2 <- df[,c(1,2)]

**UPDATE:

After changing i += 1 to i = i + 1, i get this error:

Error in paste("a", i, sep = "") <- df[, c(1, i)] : 
  target of assignment expands to non-language object

**UPDATE 2:

Based on comment i've used:

for(i in 2:length(colnames(df))){
    name <- paste("a",i,sep ="")
    name <- df[,c(1,i)]
    i = i + 1
}

But got just one data frame:

for(i in 2:length(colnames(df))){
    name <- paste("a",i,sep ="")
    assign(name) <- df[,c(1,i)]
    i = i + 1
}

But just got thi error:

Error in assign(name) <- df[, c(1, i)] : 
  could not find function "assign<-"

Answer 1

Based on @eddi answers, i arreived to this:

First answer:

for(i in 2:ncol(df)){
    assign(paste("a", i, sep=''), df[,c(1,i)])
}

But, as i wanted the column name as name for every new data frame, i've changed the code a bit:

for(i in 2:ncol(df)){
    assign(paste(as.character(colnames(df[i])), i, sep=''), df[,c(1,i)])
}

Thanks @eddi, . I didn't know about the assign function.