Re: [R] Converting a data frame to matrix

From: Petr PIKAL <petr.pikal_at_precheza.cz>
Date: Fri, 28 Mar 2008 11:55:40 +0100

Hi

r-help-bounces_at_r-project.org napsal dne 28.03.2008 10:18:20:

> Adrian Johnson wrote:
> > Hello:
> >
> > I have a tab delim file with 100 rows and 100 columns.
> >
> > I have numerical values in this table. What I want is to create an
image

Probably not. See below.

> > color map with color gradation.
> >
> > my values range from -5 to 0. max value is 0.
> >
> > to acheive this, I need to convert my data.frame into matrix.
> >
> > I tried following :
> >
> > mydf <- read.table('mytable',sep='\t',header=T)
> > mydf1 <- mydf[,2:100]
> > colnames(mydf1) <- as.character(mydf[,1])

It should be probably

rownames(mydf1) <- as.character(mydf[,1])

mydf<-rnorm(100*100)
mydf<-matrix(mydf, 100,100)
mydf<-data.frame(mydf)

mydf1<-mydf[,2:100]
colnames(mydf1)<-as.character(mydf[,1])
Error in names(x) <- value :
  'names' attribute [100] must be the same length as the vector [99]  

> >
> > here comes the trouble:
> >
> > mymat <- as.matrix(mydf1)
> >
> > -- numerical values become character values. -1 becomes "-1"

If you had all values in data frame really numeric it shall stay as numeric also in your matrix. Try

str(mydf1)

and you will probably find out that some variables are factors/character. Therefore as.matrix transfers **all** values to character as matrix can not mix data of various type.

> >
> > mymat <- data.matrix(mydf1)
> >
> > -- whole matrix is filled with 1,2 and 3.
> >
> > Is there any other way I can do this.
> >
> > say row names are city schools
> > colnames are student names
> >
> Hi Adrian,
> Have you looked at color2d.matplot in the plotrix package?
>
> Jim
>
> ______________________________________________
> 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.



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. Received on Fri 28 Mar 2008 - 10:58:10 GMT

Archive maintained by Robert King, hosted by the discipline of statistics at the University of Newcastle, Australia.
Archive generated by hypermail 2.2.0, at Fri 28 Mar 2008 - 12:30:25 GMT.

Mailing list information is available at https://stat.ethz.ch/mailman/listinfo/r-help. Please read the posting guide before posting to the list.

list of date sections of archive