ask for help

Hi everyone:
        I'm trying to compose a string dynamicly for the parameter input of
some function. For example:
In package MASS, function lda() require to input the name of predictor
variable. Let's say the 16th column is the predictor variable. Then we call
the function like this: lda(V16~., data=mydata). I don't want to hard-code
the call, instead, I would like to use a dynamic expression for this
parameter so that I can use my program on different set of data.
       I guess there,- are some function that can do this, but I didn't find
it in "Introduction to R" so far, could someone please tell me this kind of
function? Thank you!

Best,

Feng

Try:

lda(iris[-5], iris[,5])

On 12/26/06, Feng Qiu <fqiu at gatech.edu> wrote:

Hi everyone:
        I'm trying to compose a string dynamicly for the parameter input 
of
some function. For example:
In package MASS, function lda() require to input the name of predictor
variable. Let's say the 16th column is the predictor variable. Then we 
call
the function like this: lda(V16~., data=mydata). I don't want to 
hard-code
the call, instead, I would like to use a dynamic expression for this
parameter so that I can use my program on different set of data.
       I guess there,- are some function that can do this, but I didn't 
find
it in "Introduction to R" so far, could someone please tell me this kind 
of
function? Thank you!

Best,

Feng

Hi Gabor:
         Thank you!  But it didn't work.
Since lda() takes the variable
name as the input parameter.

So what I was trying to do is "make the name
dynamically". I used sprintf() to generate a variable name, such as "V16".
But it seems that the function doesn't recognize the generated name. For
example, lda(V16,data=mydata) works, But,

lda(sprintf("V%d",k),data=mydata) does not work, where k=16.  So I guess the
name generated by sprintf is not the parameter wanted. But I have no idea
about it.

Best,

Feng


----- Original Message -----
From: "Gabor Grothendieck" <ggrothendieck at gmail.com>
To: "Feng Qiu" <fqiu at gatech.edu>
Cc: <r-help at stat.math.ethz.ch>
Sent: Wednesday, December 27, 2006 1:56 PM
Subject: Re: [R] How to write string dynamicly?

Try:

lda(iris[-5], iris[,5])

On 12/26/06, Feng Qiu <fqiu at gatech.edu> wrote:

Hi everyone:
        I'm trying to compose a string dynamicly for the parameter input
of
some function. For example:
In package MASS, function lda() require to input the name of predictor
variable. Let's say the 16th column is the predictor variable. Then we
call
the function like this: lda(V16~., data=mydata). I don't want to
hard-code
the call, instead, I would like to use a dynamic expression for this
parameter so that I can use my program on different set of data.
       I guess there,- are some function that can do this, but I didn't
find
it in "Introduction to R" so far, could someone please tell me this kind
of
function? Thank you!

Best,

Feng