[R] matrix math

[Petr Pikal]

On 4 Jan 2006 at 14:10, r user wrote:

Date sent:      	Wed, 4 Jan 2006 14:10:24 -0800 (PST)
From:           	r user <ruser2006 at yahoo.com>
To:             	rhelp <r-help at stat.math.ethz.ch>
Subject:        	[R] matrix math

>   I am using R 2.1.1 in an windows XP environment.
> 
>   I have 2 dataframes, temp1 and temp2.
> 
>   Each dataframe has 20 variables (“cocolumns") and 525 observations
>   (“rows”).  All variables are numeric.
> 
>   I want to create a new dataframe that also has 20 columns and 525
>   rows.  The values in this dataframe should be the sum of the 2 other
>   dataframe.
> 
>   (i.e. temp1$column 1+temp2$column1, temp1$column2+temp2$column2,
>   etc)
> 
>   What is the best/easiest way to accomplish this?
> 
>   Is I wish to "multiply" (instead of sum) the columns, how do I?
> 
>   I tried:
> 
>   temp3<-as.matrix(temp1)+as.matrix(temp2)
> 
>   I get the following error message: “Error in as.matrix(temp1) +
>   as.matrix(temp2) : 
>           non-numeric argument to binary operator” 

Hi

although you think all variables are numeric they probably are not.

what does

str(temp1) or str(temp2)

tells you

HTH
Petr





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Petr Pikal
petr.pikal at precheza.cz