Re: [R] Using image function to plot character values

From: Jim Lemon <>
Date: Fri, 25 Apr 2008 19:32:00 +1000

Eric Bell wrote:
> Hello. I am a newbie to R. If I should be reading some FAQ or manual
> that could help answer my question please tell me and I will go there.
> Problem:
> I have a spreadsheet that contains a character code in each cell. The
> columns in the spreadsheet represent time and the rows represent people.
> I want to use the image function to display this information, but the
> image function requires numeric data. I know how to read in the
> spreadsheet into a data frame, but if I use data.matrix to convert data
> frame into a numeric matrix, each column gets converted separately, so
> that the same character code may get converted to a different numeric
> code depending on the column. How do I apply the character to numeric
> conversion so that each character gets converted to the same numeric
> value?
> A secondary problem is that after I do the conversion, I need to know
> what codes were converted to what numeric values.
Hi Eric,
Using your example data frame,


gives you the matrix you want, and


gives you the correspondence between character codes and numbers.

Jim mailing list PLEASE do read the posting guide and provide commented, minimal, self-contained, reproducible code. Received on Fri 25 Apr 2008 - 09:38:30 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 25 Apr 2008 - 10:30:31 GMT.

Mailing list information is available at Please read the posting guide before posting to the list.

list of date sections of archive