[R] Adding Column to Data Frames Using a Loop

[Sparks, John James]

Dear R Helpers,

I am trying to do calculations on multiple data frames and do not want to
create a list of them to go through each one.  I know that lists have many
wonderful advantages, but I believe the better thing is to work df by df
for my particular situation.  For background, I have already received some
wonderful help on how to handle some situations, such as removing columns:


x=as.data.frame(matrix(c(1,2,3,
        1,2,3,
        1,2,2,
        1,2,2,
       1,1,1),ncol=3,byrow=T))

y=as.data.frame(matrix(c(1,2,3,
        1,2,3,
        1,2,2,
        1,2,2,
       1,1,1),ncol=3,byrow=T))

z=as.data.frame(matrix(c(1,2,3,
        1,2,3,
        1,2,2,
        1,2,2,
       1,1,1),ncol=3,byrow=T))

for(i in letters[24:26] ) assign( i, subset(get(i), select=-c(V1))  )
x
y
z

And I figured how to do further processing using functions:

myfunc<-function(DF){
 DF$V4<-DF$V2+DF$V3
 return(DF)
}
for(i in letters[24:26] ) assign( i, myfunc(get(i)))

But if I want to do a rather simple calculation and store it as a new
column in each data frame such as

x$V4<-x$V2+x$V3
y$V4<-y$V2+y$V3
z$V4<-z$V2+z$V3

is there a simpler way to do this than building a function as shown above?
 I tried a few variations of

i<-24
assign(paste(i,"$V4",sep=""),paste(get(i),"$V2+",get(i),"$V3",sep=""))

but keep getting syntax errors.

If anyone could help with the syntax as to how to accomplish the
calculation above without building a function, I would really appreciate
it.

--John Sparks