[R] Plots from categorial data

[Christoph Krammer]

Hello Hadley,

Thanks a lot for your help. I got the plot I want out of this module with a
slightly more complicated command.

But now, I have an additional problem: 

In the given case, the "filtersetting" column contains letters, so R takes
the values as categories. But I have other filters, which only have numeric
categories like "0.125", "0.25", "1", and so on. But there is no real
"distance" between these values, so the data is still categorial. But if I
draw a plot from this data, the result is a plot with axis labels like 0.2,
0.4, 0.6, ...

How do I tell R to treat the numbers in the filtersetting column as
categories?

Thanks and regards,
 Christoph


-----Ursprüngliche Nachricht-----
Von: hadley wickham [mailto:h.wickham at gmail.com] 
Gesendet: Sonntag, 1. Juli 2007 12:21
An: Christoph Krammer
Cc: r-help at stat.math.ethz.ch
Betreff: Re: [R] Plots from categorial data

Perhaps this will do what you want:

library(ggplot2)
qplot(filter_setting, avg.hit, data=data, colour=ocrtool, geom="line")

find out more about ggplot2 at http://had.co.nz/ggplot2

Hadley

On 7/1/07, Christoph Krammer <ck at altaica.de> wrote:
> Hello everybody,
>
> Since my first message was caught by the spam filter, I just try to do 
> it
> again:
>
> I want to use R to generate plots from categorial data. The data 
> contains results from OCR scans over images with are preprocessed by 
> different image filtering techniques. A small sample data set looks as
following:
>
> > data <- read.csv("d:/tmp_da/sql_data/filter_d_tool.csv", header=T) 
> > data
>       ocrtool filter_setting avg.hit.
> 1  FineReader            2x1    0.383
> 2  FineReader            2x2    0.488
> 3  FineReader            3x2    0.268
> 4  FineReader            3x3    0.198
> 5  FineReader            4x3    0.081
> 6  FineReader            4x4    0.056
> 7        gocr            2x1    0.153
> 8        gocr            2x2    0.102
> 9        gocr            3x2    0.047
> 10       gocr            3x3    0.052
> 11       gocr            4x3    0.014
> 12       gocr            4x4    0.002
> 13      ocrad            2x1    0.085
> 14      ocrad            2x2    0.094
> 15      ocrad            3x2    0.045
> 16      ocrad            3x3    0.050
> 17      ocrad            4x3    0.025
> 18      ocrad            4x4    0.009
>
>
> I now want to draw a plot with the categories (filter_setting) as X 
> axis, and the avg_hit as Y axis. There should be lines for each ocrtool.
>
> But when I draw a plot, the resulting plot always contains bars, even 
> if I specify type="n".
> > plot(data$filter_setting, data$avg.hit., type="n")
>
> When I only plot the categories, without data, there appear strange 
> grey (but empty) boxes.
> > plot(data$filter_setting, type="n")
>
> Who do I get a clean white box to draw the different lines in?
>
> Thanks and regards,
>  Christoph
>
> ---
> Christoph Krammer
> Student
>
> University of Mannheim
> Laboratory for Dependable Distributed Systems A5, 6
> 68131 Mannheim
> Germany
>
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