extracting data from a dataframe

Hi everyone,

Here's a question about extracting data from a dataframe:

Let's say I've got a dataframe with two vectors, TEST and GENDER. GENDER
contains a 1 for males and 2 for females. I want to separate the results
of TEST by GENDER so I can compare their means.

What's the most efficient way to do this with R?

No guarantees of efficiency, but the easiest is
  split(df$TEST,df$GENDER)

	-thomas


-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._

"tim" == Tim Wilson <wilson at visi.com> writes:

tim> Hi everyone,
    tim> Here's a question about extracting data from a dataframe:

    tim> Let's say I've got a dataframe with two vectors, TEST and GENDER. GENDER
    tim> contains a 1 for males and 2 for females. I want to separate the results
    tim> of TEST by GENDER so I can compare their means.

    tim> What's the most efficient way to do this with R?

something like:

lapply(split(df$TEST,df$GENDER),mean)

?
(where "df" is the data.frame).

A.J. Rossini				Rsrch. Asst. Prof. of Biostatistics
U. of Washington Biostatistics		rossini at u.washington.edu	
FHCRC/SCHARP/HIV Vaccine Trials Net	rossini at scharp.org
-------------- http://software.biostat.washington.edu/ ----------------
FHCRC: M: 206-667-7025 (fax=4812)|Voicemail is pretty sketchy/use Email
UW:   Th: 206-543-1044 (fax=3286)|Change last 4 digits of phone to FAX
(my tuesday/wednesday/friday locations are completely unpredictable.)



-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._

-----Original Message-----
Hi everyone,

Here's a question about extracting data from a dataframe:

Let's say I've got a dataframe with two vectors, TEST and GENDER.
GENDER
contains a 1 for males and 2 for females. I want to separate the

results

of TEST by GENDER so I can compare their means.

What's the most efficient way to do this with R?

-Tim

Presuming that you wish to perform a two-sample t-test on the means, you
don't need to actually "split" the dataframe. You could use the formula
method for t.test() by the following:

t.test(df$TEST ~ df$GENDER)

where df is the name of your dataframe.

If you actually want to split the dataframe, see ?split.

HTH.

Marc


-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._

Hi, dear R

I am dealing with my dataset with strong collinearity. I want to use the
Variance Decomposition (Variance Proportion) method. There is a process in
SAS called PROC REG to do it. I wonder if I can find a function in R or
Splus to carry out as well.

Thanks a lot!

Huan

-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._