R help - Jun 2008 - Adding new columns to (output) data - e.g., read 5 cols write 8

Hello, I have the following task I'd like to accomplish:

A file contains 5 columns of data (several hundred rows), let's call
them a, b, c, d and e (ie these are their column headers)

I also have a set of definitions, e.g.,

f = a + b
g = a * 3
h = c + d
etc.

I would like to write out a new .rda file that contains columns

a b c d e f g h etc.

I.e. , the original data plus new columns (with headers and data).

It seems that there ought to be a simple way to do this, could
someone provide some guidance on the best way to accomplish
this task? (I tried a few things as this seemed rather trivial,
but did not succeed. I still hope/assume this is a trivial thing
to do if one knows R well)

Thanks,

Esmail

ps: I want to thank everyone again who posted their solutions
     to my previous query. Seeing different solutions for the same
     problem is a tremendously effective way to learn something
     new.

yourDF <- cbind(yourDF, f=yourDF$a+yourDF$b, g=yourDF$a * 3,
h=yourDF$c + yourDF$d)

On Wed, Jun 11, 2008 at 9:26 PM, Esmail Bonakdarian <esmail.js at
gmail.com> wrote:
> Hello, I have the following task I'd like to accomplish:
>
> A file contains 5 columns of data (several hundred rows), let's call
> them a, b, c, d and e (ie these are their column headers)
>
> I also have a set of definitions, e.g.,
>
> f = a + b
> g = a * 3
> h = c + d
> etc.
>
> I would like to write out a new .rda file that contains columns
>
> a b c d e f g h etc.
>
> I.e. , the original data plus new columns (with headers and data).
>
> It seems that there ought to be a simple way to do this, could
> someone provide some guidance on the best way to accomplish
> this task? (I tried a few things as this seemed rather trivial,
> but did not succeed. I still hope/assume this is a trivial thing
> to do if one knows R well)
>
> Thanks,
>
> Esmail
>
> ps: I want to thank everyone again who posted their solutions
>    to my previous query. Seeing different solutions for the same
>    problem is a tremendously effective way to learn something
>    new.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem you are trying to solve?

Esmail -

Esmail Bonakdarian wrote:
> Hello, I have the following task I'd like to accomplish:
> 
> A file contains 5 columns of data (several hundred rows), let's call
> them a, b, c, d and e (ie these are their column headers)
Are these 5 vectors of data stored in a data.frame?  I assume so.
> 
> I also have a set of definitions, e.g.,
> 
> f = a + b
> g = a * 3
> h = c + d
> etc.
> 
> I would like to write out a new .rda file that contains columns
> 
> a b c d e f g h etc.
> 
> I.e. , the original data plus new columns (with headers and data).
Example,

test <- data.frame(a = 1:10, b = 2:11, c = 3:12)
test2 <- transform(test, d = 2*a + b, e = 3*c)
save(test2, file = "test2.Rdata")

Does this help?

Best,
Erik Iverson

jim holtman wrote:
> yourDF <- cbind(yourDF, f=yourDF$a+yourDF$b, g=yourDF$a * 3,
> h=yourDF$c + yourDF$d)
Thanks Jim, I also learned about the transform() method from Erik
which will also work beautifully.

Esmail