I could not get Jim code to work (can't install colors in R 2.13). However
Alexander code seems what I want. Just a litle detail, I need all bars with
same size, the only difference between they are the colors.



On Thu, Jul 28, 2011 at 6:11 AM, Jim Lemon <jim@bitwrit.com.au> wrote:

> On 07/28/2011 11:25 AM, Fernando Andreacci wrote:
>
>> I have a simple bar chart with annual precipitation (jan to dez).
>>
>> I want to plot, above each bar (on a line), a square wich is color based
>> on
>> a scale (0-100%). With 0 being white and 100 black, like a gradient. Is it
>> possible? How to?
>>
>
> Hi Fernando,
> I think you want the grayscale to reflect the values of the percentages, so
> here is one way to do it:
>
> # make up some values for the bars
> barvalues<-sample(0:9,10)
> # make up some values for the percentages
> pctvalues<-sample(0:100,10)
> # draw a barplot
> xpos<-barplot(barvalues,ylim=**c(0,10))
> # translate the percent values into grayscale
> pctcolors<-color.scale(**pctvalues)
> rect(xpos-0.3,barvalues+0.5,**xpos+0.3,barvalues+1,col=**pctcolors)
>
> Jim
>



-- 
Fernando Andreacci
Biólogo
Fone +55 47 9921 4015
        +55 41 9921 3934
fandreacci@gmail.com

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