O.9: using alpha() in scale_colour_manual?

[Matthieu Stigler]

Hi

I am using now version 0.9 and face a problem with the alpha() function
for scale_fill_manual: it simply does not seem to work... and the
transparency is not recognised?

See:
library(ggplot2)
library(scales)

df<-data.frame(a=1:3, b=factor(letters[1:3]))
cols<-c(alpha("red", .3),alpha("red", 0.6),alpha("red", 0.9))

plot(1:3, col=cols, cex=20, pch=19) # yes colours are different!
qplot(b,a, data=df, fill=b, geom="bar",
stat="identity")+scale_fill_manual(values = cols) #same colour?

I see the same colour for each bar... is this normal? Thanks!!

Matthieu

[Dennis Murphy]

Hi:

I couldn't get it to work nicely with qplot(), but did manage with ggplot():

df<-data.frame(a=1:3, b=factor(letters[1:3]))

ggplot(data = df, aes(x = b, y = a)) +
geom_bar(aes(alpha = b), fill = 'red', stat = 'identity') +
scale_alpha_manual(values = c(0.3, 0.6, 0.9))

Question for the gurus: Why do points get plotted with this code???

qplot(b, a, data = df) +
geom_bar(aes(alpha = b), fill = 'red', stat = 'identity') +
scale_alpha_manual(values = c(0.3, 0.6, 0.9))

Dennis

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[Matthieu Stigler]

Dennis

Thanks for your help!

So basically it seems scale_fill_manual() in 0.9 is no longer able to
support alpha levels, and these need to be specified through
scale_alpha_manual? It looks to me this should be considered a bug?

Thanks!

Matthieu

Le 30/03/2012 11:13, Dennis Murphy a �crit :

[Jean-Olivier Irisson]

On 2012-Apr-02, at 09:22 , Matthieu Stigler wrote:
>
> So basically it seems scale_fill_manual() in 0.9 is no longer able to support alpha levels, and these need to be specified through scale_alpha_manual? It looks to me this should be considered a bug?

If the only thing you want to vary in a scale is alpha and that the variation maps to some of your data, then scale_alpha* is the way to go indeed.

If you want to vary both alpha and colour based on your data, mix scale_fill and scale_alpha

If you want to vary colour but have all bars be a bit transparent (with the same transparency) then *map* colour (within aes + use scale_fill) and *set* alpha (outside aes).
scale_fill* did not handle setting alpha in 0.9.0 and this was a bug; it should be fixed in the devel version.

Jean-Olivier Irisson
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