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Newbie hung up with matrices

5 messages · rwatkins@cornerstonelp.com, Brian Ripley, Chuck Cleland +2 more

rwatkins@cornerstonelp.com
# 
Hi all:
	Thanks in advance for your assistance.

	I just started learning R.  I'm trying to use the Help and the downloadable
manuals.  I am stuck on trying to multiply matrices.  Can anyone please
supply a couple of lines of code that I can plug into a fresh console to see
how  a double precision (1x3) matrix is multiplied by a double precision
(3x3) matrix?  I keep getting an error message,"Error in x%*%A: requires
numeric matrix/vector arguments".

	I have some VBA and VB experience (thus a little Object Oriented
programming experience), am I right in beliving that I am not "dimensioning"
correctly?  I have been trying the following example:
		A<-matrix
		A<-read.csv("test33.csv"), where the data is
				A,B,C
				1,4,7
				2,5,8
				3,6,9

		x<-c(4,5,6)
		x%*%A
			ERROR (as shown above)

	ALSO, I have downloaded the RExcel add-in, but have not found any reference
manual, etc that describes how to use it.  Any suggestions here are
appreciated, as I primarily do my work in Excel.

	Are there any good books available that will help me in my quest to become
a more adept user of R?  I know I am going to need this package for
multivariate regressions, etc.

	Again, thanks in advance for your time and consideration.
Brian Ripley
#
On Fri, 16 May 2003 rwatkins at cornerstonelp.com wrote:

            

      
      
      
    

        
You've forgotten header=TRUE, if you don't want A,B,C to be part of your 
matrix.  R comes with a Data Import/Export Manual: please consult it.

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Chuck Cleland
    

    

      
      #
    

  


  

      
rwatkins at cornerstonelp.com wrote:

            

      
      
      
    

        
> A <- matrix(c(1,4,7,2,5,8,3,6,9), ncol=3, byrow=TRUE)
 > x <- c(3,5,6)
 > x%*%A
      [,1] [,2] [,3]
[1,]   31   73  115

The result of read.csv is not a matrix, so try the following:

A <- as.matrix(A)
x%*%A

hope this helps,

Chuck Cleland

  
  


  


      

    

    

      
      

        


  

        

      Marc Feldesman
    

    

      
      #
    

  


  

      
On Fri, 16 May 2003 12:00:42 -0500, an incredible array of electrons
randomly cascading around the Universe collided and turned into words
spewed forth by rwatkins at cornerstonelp.com:


rwatkins at cornerstonelp.com> Hi all:
rwatkins at cornerstonelp.com> 	Thanks in advance for your assistance.
rwatkins at cornerstonelp.com> 
rwatkins at cornerstonelp.com> 	I just started learning R.  I'm trying
to use the Help and the downloadable
rwatkins at cornerstonelp.com> manuals.  I am stuck on trying to multiply
matrices.  Can anyone please
rwatkins at cornerstonelp.com> supply a couple of lines of code that I
can plug into a fresh console to see
rwatkins at cornerstonelp.com> how  a double precision (1x3) matrix is
multiplied by a double precision
rwatkins at cornerstonelp.com> (3x3) matrix?  I keep getting an error
message,"Error in x%*%A: requires
rwatkins at cornerstonelp.com> numeric matrix/vector arguments".
rwatkins at cornerstonelp.com> 
rwatkins at cornerstonelp.com> 	I have some VBA and VB experience
(thus a little Object Oriented
rwatkins at cornerstonelp.com> programming experience), am I right in
beliving that I am not "dimensioning"
rwatkins at cornerstonelp.com> correctly?  I have been trying the
following example:
rwatkins at cornerstonelp.com> 		A<-matrix
rwatkins at cornerstonelp.com> 		A<-read.csv("test33.csv"), where the
data is
rwatkins at cornerstonelp.com> 				A,B,C
rwatkins at cornerstonelp.com> 				1,4,7
rwatkins at cornerstonelp.com> 				2,5,8
rwatkins at cornerstonelp.com> 				3,6,9
rwatkins at cornerstonelp.com> 
rwatkins at cornerstonelp.com> 		x<-c(4,5,6)
rwatkins at cornerstonelp.com> 		x%*%A
rwatkins at cornerstonelp.com> 			ERROR (as shown above)
rwatkins at cornerstonelp.com> 
rwatkins at cornerstonelp.com> 	ALSO, I have downloaded the RExcel
add-in, but have not found any reference
rwatkins at cornerstonelp.com> manual, etc that describes how to use it. 
Any suggestions here are
rwatkins at cornerstonelp.com> appreciated, as I primarily do my work in
Excel.
rwatkins at cornerstonelp.com> 
rwatkins at cornerstonelp.com> 	Are there any good books available
"that will help me in my quest to become
rwatkins at cornerstonelp.com> a more adept user of R?  I know I am going
to need this package for
rwatkins at cornerstonelp.com> multivariate regressions, etc.
rwatkins at cornerstonelp.com> 
rwatkins at cornerstonelp.com> 	Again, thanks in advance for your time
and consideration.
rwatkins at cornerstonelp.com> 
rwatkins at cornerstonelp.com>
______________________________________________


Couple of thoughts.

A<-matrix      # what's the purpose???

A<-read.csv("test33.csv", header=TRUE)

A  # just to list your data

and to make sure that A,B,C aren't stuck in there as rows.

Then your command should work (also assuming that you really have
a CSV file).  Try ?read.csv

Hope this helps.

  
  


  


      

    

    

      
      

        


  

        

      Jerome Asselin
    

    

      
      #
    

  


  

      
You need to convert your data frame as a matrix before your operation. Try 
this:
x %*% as.matrix(A)

Regarding a good book, I may not be the best person to answer you. I am 
aware of the online manuals available at http://www.r-project.org .
The manual "An Introduction to R" is my personal best bet.

HTH,
Jerome

        
On May 16, 2003 10:00 am, rwatkins at cornerstonelp.com wrote: