R help - Sep 2006 - Variable as color in a barplot

Dear wise ones,

I have a problem assigning different colors to bars in a barplot.
The data I'm using is the following dataframe (truncated) :

 > L0
       r n p   t
[...]
18   19 1 1 RFM
19   20 1 1 RFM
20   21 2 1 RFM
21   23 6 1 RIH
22   24 2 1 ROC
23   25 1 1 ROC
24   26 1 1 ROC
25   27 2 1 ROC
26   28 2 1 RFT
27   29 1 1 RFT
28   30 2 1 RFT
29   31 1 1 ROH
[...]

My barplot should display ascending bars according to L0$n. Their width 
depends on L0$p, which can be greater than 1. Last, I want a different 
color for each of the five values of L0$t.
I use the following array to assign a colour for each type given in 
L0$t :

 > coul <- array()
 > coul['ROC'] <- 'khaki1'
 > coul['RFM'] <- 'palegreen'
 > coul['RFT'] <- 'lightorange'
 > coul['RIH'] <- 'blue'
 > coul['ROH'] <- 'lightblue'

And here's the barplot command I'm using :

 > barplot(sort(L0$n), ylim=c(0,10), width=L0$p[order(L0$n)], 
col=coul[L0$t[order(L0$n)]], main="Nombre de genres",
sub="Livrets")

The barplot uses the sort() and order() functions to display ascending 
bars with the right values. The width parameter works fine, but the 
color doesn't. I get :

Erreur dans rect(y1, x1, y2, x2, ...) : nom de couleur incorrect
(error in rect(y1, x1, y2, x2, ...) : incorrect color name)

I tried to fiddle with coul[] or its indice but it didn't help.
Does anybody know what's wrong ?
Many thanks,

Octave

I think it is because your command:
 > coul <- array()
means that the first element of coul is NA, even after you've added the
colour names.

On 22/09/06, Octave Julien <ktawo@free.fr> wrote:
>
> Dear wise ones,
>
> I have a problem assigning different colors to bars in a barplot.
> The data I'm using is the following dataframe (truncated) :
>
> > L0
>        r n p   t
> [...]
> 18   19 1 1 RFM
> 19   20 1 1 RFM
> 20   21 2 1 RFM
> 21   23 6 1 RIH
> 22   24 2 1 ROC
> 23   25 1 1 ROC
> 24   26 1 1 ROC
> 25   27 2 1 ROC
> 26   28 2 1 RFT
> 27   29 1 1 RFT
> 28   30 2 1 RFT
> 29   31 1 1 ROH
> [...]
>
> My barplot should display ascending bars according to L0$n. Their width
> depends on L0$p, which can be greater than 1. Last, I want a different
> color for each of the five values of L0$t.
> I use the following array to assign a colour for each type given in
> L0$t :
>
> > coul <- array()
> > coul['ROC'] <- 'khaki1'
> > coul['RFM'] <- 'palegreen'
> > coul['RFT'] <- 'lightorange'
> > coul['RIH'] <- 'blue'
> > coul['ROH'] <- 'lightblue'
>
> And here's the barplot command I'm using :
>
> > barplot(sort(L0$n), ylim=c(0,10), width=L0$p[order(L0$n)],
> col=coul[L0$t[order(L0$n)]], main="Nombre de genres",
sub="Livrets")
>
> The barplot uses the sort() and order() functions to display ascending
> bars with the right values. The width parameter works fine, but the
> color doesn't. I get :
>
> Erreur dans rect(y1, x1, y2, x2, ...) : nom de couleur incorrect
> (error in rect(y1, x1, y2, x2, ...) : incorrect color name)
>
> I tried to fiddle with coul[] or its indice but it didn't help.
> Does anybody know what's wrong ?
> Many thanks,
>
> Octave
>
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>


-- 
================================David Barron
Said Business School
University of Oxford
Park End Street
Oxford OX1 1HP

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