R help - Jun 2009 - The most straightfoward way to write a function that sums over the rows of a matrix

Hello!

 

I am trying to write a function with vector and data.frame parameters that
uses the sum() function and values from the rows of the data.frame.

I need to pass this function as a parameter to optim().

 

My starting point is:

observs <- data.frame(y, x1, x2, x3)

 

Fn <- function(par, observs) {

                sum( (y - (par[1] * (x1 + 1) * x2^(-par[2]) * x3^par[3])^2 )

}

 

y, x1, x2, x3 are all vectors.

 

I am a bit new to R and I have not been able to find a good description of
how to iterate over rows in a data.frame.

 

What is a straightforward way to do this?

What am I missing?

 

Thanks

Stu

 


	[[alternative HTML version deleted]]

Why not just use rowSums?

Ronggui

2009/6/16 Stu @ AGS <stu at agstechnet.com>:
> Hello!
>
>
>
> I am trying to write a function with vector and data.frame parameters that
> uses the sum() function and values from the rows of the data.frame.
>
> I need to pass this function as a parameter to optim().
>
>
>
> My starting point is:
>
> observs <- data.frame(y, x1, x2, x3)
>
>
>
> Fn <- function(par, observs) {
>
> ? ? ? ? ? ? ? ?sum( (y - (par[1] * (x1 + 1) * x2^(-par[2]) * x3^par[3])^2 )
>
> }
>
>
>
> y, x1, x2, x3 are all vectors.
>
>
>
> I am a bit new to R and I have not been able to find a good description of
> how to iterate over rows in a data.frame.
>
>
>
> What is a straightforward way to do this?
>
> What am I missing?
>
>
>
> Thanks
>
> Stu
>
>
>
>
> ? ? ? ?[[alternative HTML version deleted]]
>
> ______________________________________________
> 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.
>


-- 
HUANG Ronggui, Wincent
PhD Candidate
Dept of Public and Social Administration
City University of Hong Kong
Home page: http://asrr.r-forge.r-project.org/rghuang.html

The apply function is the way to iterate over rows or columns of  
dataframes or matrices. An example would have made this process easier  
testing and I have given up doing that job for

You might try:

apply(observs, 1, function(x)  Fn(par, x) )

On Jun 16, 2009, at 11:08 AM, Stu @ AGS wrote:
> Hello!
>
>
>
> I am trying to write a function with vector and data.frame  
> parameters that
> uses the sum() function and values from the rows of the data.frame.
>
> I need to pass this function as a parameter to optim().
>
>
>
> My starting point is:
>
> observs <- data.frame(y, x1, x2, x3)
>
>
>
> Fn <- function(par, observs) {
>
>                sum( (y - (par[1] * (x1 + 1) * x2^(-par[2]) *  
> x3^par[3])^2 )
>
> }
>
>
>
> y, x1, x2, x3 are all vectors.
>
>
>
> I am a bit new to R and I have not been able to find a good  
> description of
> how to iterate over rows in a data.frame.
>
>
>
> What is a straightforward way to do this?
>
> What am I missing?
>
>
>
> Thanks
>
> Stu
>
>
>
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> 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.
David Winsemius, MD
Heritage Laboratories
West Hartford, CT

Patrick,
	Thanks for your suggestion!
	The R-Inferno was especially useful!!  The first chapter had me
chuckling aloud despite the fact that I work alone.
	Well worth the price!

Thanks!
Stu
> -----Original Message-----
> From: Patrick Burns [mailto:pburns at pburns.seanet.com]
> Sent: Tuesday, June 16, 2009 11:31 AM
> To: Stu @ AGS
> Subject: Re: [R] The most straightfoward way to write a function that
> sums over the rows of a matrix
> 
> 'The R Inferno' may be of use to you.
> 
> 
> 
> Patrick Burns
> patrick at burns-stat.com
> +44 (0)20 8525 0696
> http://www.burns-stat.com
> (home of "The R Inferno" and "A Guide for the Unwilling S
User")
> 
>