[R] Newbie hung up with matrices

Jerome Asselin jerome at hivnet.ubc.ca
Fri May 16 20:41:16 CEST 2003

You need to convert your data frame as a matrix before your operation. Try 
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.


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