thr3ads.net - R help - [R] Function call within a function. [Jun 2007]

If this information is useful, please help other people find it:
Share via:

John Kane

2007-Jun-28 19:03 UTC

[R] Function call within a function.

I am trying to call a funtion within another function
and I clearly am misunderstanding what I should do. 
Below is a simple example.
I know lstfun works on its own but I cannot seem to
figure out how to get it to work within ukn. Basically
I need to create the variable "nts". I have probably
missed something simple in the Intro or FAQ.

Any help would be much appreciated.

EXAMPLE
-------------------------------------------------------------------------------
# create data.frame
cata <- c( 1,1,6,1,1,4)
catb <- c( 1,2,3,4,5,6)
id <- c('a', 'b', 'b', 'a', 'a',
'b')
dd1  <-  data.frame(id, cata,catb)

# function to create list from data.frame
lstfun  <- function(file, alpha , beta ) {
cda  <-  subset(file, file[,1] == alpha)
cdb  <-  subset (file, file[,1]== beta)
list1 <- list(cda,cdb)
}

# funtion to operate on list
ukn  <-  function(file, alpha, beta, nam1){
aa  <- alpha
bb  <- beta
myfile  <- file
nts <- lstfun(myfile, aa, bb)
mysum <- nam1[,3]*5
return(mysum)
}

results <- ukn(dd1, "a", "b", nts$cda)

Nordlund, Dan (DSHS/RDA)

2007-Jun-28 21:08 UTC

head link

[R] Function call within a function.

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of John Kane
> Sent: Thursday, June 28, 2007 12:04 PM
> To: R R-help
> Subject: [R] Function call within a function.
> 
> I am trying to call a funtion within another function
> and I clearly am misunderstanding what I should do. 
> Below is a simple example.
> I know lstfun works on its own but I cannot seem to
> figure out how to get it to work within ukn. Basically
> I need to create the variable "nts". I have probably
> missed something simple in the Intro or FAQ.
> 
> Any help would be much appreciated.
> 
> EXAMPLE
> --------------------------------------------------------------
> -----------------
> # create data.frame
> cata <- c( 1,1,6,1,1,4)
> catb <- c( 1,2,3,4,5,6)
> id <- c('a', 'b', 'b', 'a', 'a',
'b')
> dd1  <-  data.frame(id, cata,catb)
> 
> # function to create list from data.frame
> lstfun  <- function(file, alpha , beta ) {
> cda  <-  subset(file, file[,1] == alpha)
> cdb  <-  subset (file, file[,1]== beta)
> list1 <- list(cda,cdb)
> }
> 
> # funtion to operate on list
> ukn  <-  function(file, alpha, beta, nam1){
> aa  <- alpha
> bb  <- beta
> myfile  <- file
> nts <- lstfun(myfile, aa, bb)
> mysum <- nam1[,3]*5
> return(mysum)
> }
> 
> results <- ukn(dd1, "a", "b", nts$cda)
John,

The first problem I see is one of scope.  nts$cda refers to an object called nts
which does not exist in the calling environment (it is local to the function
ukn).  So trying to call ukn() with nts results in an error.  Second, even if
you pass the name of the object, you will not be able to use it in ukn() in the
manner that you are trying.  Your ukn() function definition also requires that
it know the inner workings of function lstfun().  Functions generally
shouldn't require knowing how other functions work, they should only rely on
what value is returned.

You can get what you want by redefining ukn in the following way

# funtion to operate on list
ukn  <-  function(file, alpha, beta, nam1){
aa  <- alpha
bb  <- beta
myfile  <- file
nts <- lstfun(myfile, aa, bb)
mysum <- nts[[nam1]][,3]*5
return(mysum)
}

And change the function call to

results <- ukn(dd1, "a", "b", 1) 

This still leaves the functions coupled in a way that I don't like, but
I'm not a good enough R programmer to solve that problem at the moment. 
Maybe someone else will come along with a better solution.

Hope this is helpful,

Dan

Daniel J. Nordlund
Research and Data Analysis
Washington State Department of Social and Health Services
Olympia, WA  98504-5204

Jason Barnhart

2007-Jun-28 21:40 UTC

head link

[R] Function call within a function.

The problem isn't the function call.

First, list1 returned by lstfun does not name its elements so nts$cda 
won't work. See code change in lstfun.

Second, specifying nts$cda as the nam1 argument tells R to look for 
the nts object in the environment in which ukn is called.  However, 
the nts object is not created in the parent environment, it is created 
in the ukn's environment.

Third, nam1[,3] should be nam1[2] as there is no third element to this 
list (although and this doesn't resolve the environment issue).

I've modified your code below to work, but there are better ways to go 
about this.  Thomas Lumley has a famous quote regarding parse.  See 
http://tolstoy.newcastle.edu.au/R/e2/help/07/01/8059.html among 
others.

I was once referred to Patrick Burns' S Poetry to learn about the 
"eval(parse(text=)))" paradigm which was very helpful. You may also 
want to brush up on environments (see ?environment) to learn more 
about lexical scoping.

Hope this helps.
-jason

#MODIFIED CODE
# create data.frame
cata <- c( 1,1,6,1,1,4)
catb <- c( 1,2,3,4,5,6)
id <- c('a', 'b', 'b', 'a', 'a',
'b')
dd1 <- data.frame(id, cata,catb)

# function to create list from data.frame
lstfun <- function(file, alpha , beta ) {
cda <- subset(file, file[,1] == alpha)
cdb <- subset (file, file[,1]== beta)
### CODE ADDED HERE
list1 <- list(cda=cda,cdb=cdb)
}

# funtion to operate on list
ukn <- function(file, alpha, beta, nam1){
aa <- alpha
bb <- beta
myfile <- file
nts <- lstfun(myfile, aa, bb)
### CODE ADDED HERE
mysum <- eval(parse(text=nam1))
#mysum <- nam1[,3]*5
return(mysum)
}

results <- ukn(dd1, "a", "b", "nts$cda") ###
modified how called.

----- Original Message ----- 
From: "John Kane" <jrkrideau at yahoo.ca>
To: "R R-help" <r-help at stat.math.ethz.ch>
Sent: Thursday, June 28, 2007 12:03 PM
Subject: [R] Function call within a function.

>I am trying to call a funtion within another function
> and I clearly am misunderstanding what I should do.
> Below is a simple example.
> I know lstfun works on its own but I cannot seem to
> figure out how to get it to work within ukn. Basically
> I need to create the variable "nts". I have probably
> missed something simple in the Intro or FAQ.
>
> Any help would be much appreciated.
>
> EXAMPLE
>
-------------------------------------------------------------------------------
> # create data.frame
> cata <- c( 1,1,6,1,1,4)
> catb <- c( 1,2,3,4,5,6)
> id <- c('a', 'b', 'b', 'a', 'a',
'b')
> dd1  <-  data.frame(id, cata,catb)
>
> # function to create list from data.frame
> lstfun  <- function(file, alpha , beta ) {
> cda  <-  subset(file, file[,1] == alpha)
> cdb  <-  subset (file, file[,1]== beta)
> list1 <- list(cda,cdb)
> }
>
> # funtion to operate on list
> ukn  <-  function(file, alpha, beta, nam1){
> aa  <- alpha
> bb  <- beta
> myfile  <- file
> nts <- lstfun(myfile, aa, bb)
> mysum <- nam1[,3]*5
> return(mysum)
> }
>
> results <- ukn(dd1, "a", "b", nts$cda)
>
> ______________________________________________
> R-help at stat.math.ethz.ch 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.
>

Stephen Tucker

2007-Jun-28 22:00 UTC

head link

[R] Function call within a function.

Dear John,

Perhaps I am mistaken in what you are trying to accomplish but it seems like
what is required is that you call lstfun() outside of ukn(). [and remove the
call to lstfun() in ukn()].

nts <- lstfun(myfile, aa, bb)
results <- ukn(dd1, "a", "b", nts$cda)

Alternatively, you can eliminate the fourth argument in ukn() and assign (via
'<-') the results of lstfun() to 'nam1' within ukn() instead
of saving to
'nts'...

--- John Kane <jrkrideau at yahoo.ca> wrote:
> I am trying to call a funtion within another function
> and I clearly am misunderstanding what I should do. 
> Below is a simple example.
> I know lstfun works on its own but I cannot seem to
> figure out how to get it to work within ukn. Basically
> I need to create the variable "nts". I have probably
> missed something simple in the Intro or FAQ.
> 
> Any help would be much appreciated.
> 
> EXAMPLE
>
-------------------------------------------------------------------------------> # create data.frame
> cata <- c( 1,1,6,1,1,4)
> catb <- c( 1,2,3,4,5,6)
> id <- c('a', 'b', 'b', 'a', 'a',
'b')
> dd1  <-  data.frame(id, cata,catb)
> 
> # function to create list from data.frame
> lstfun  <- function(file, alpha , beta ) {
> cda  <-  subset(file, file[,1] == alpha)
> cdb  <-  subset (file, file[,1]== beta)
> list1 <- list(cda,cdb)
> }
> 
> # funtion to operate on list
> ukn  <-  function(file, alpha, beta, nam1){
> aa  <- alpha
> bb  <- beta
> myfile  <- file
> nts <- lstfun(myfile, aa, bb)
> mysum <- nam1[,3]*5
> return(mysum)
> }
> 
> results <- ukn(dd1, "a", "b", nts$cda)
> 
> ______________________________________________
> R-help at stat.math.ethz.ch 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.
>

Maybe Matching Threads

Search for more seemingly similar threads

R help - Jun 2007 - Function call within a function.

[R] Function call within a function.

[R] Function call within a function.

[R] Function call within a function.

[R] Function call within a function.

Maybe Matching Threads