No control of alpha with filled points
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Winston Chang
Jun 5, 2009, 2:26:48 AM6/5/09
to ggplot2
Because I like the way they look for plots with points and lines, I've been making some graphs with the filled shapes (21-25). This is a pretty minor bug, but I've found that the fill doesn't seem to follow the specified alpha level, although the outline does. Or maybe it's a feature.
Attached are a scatterplot (generated by the code below) and a zoomed-in view of a PDF with these shapes. In the zoomed-in view, you can see the edge of the white circle underneath the green ring.
df <- data.frame(xval=rnorm(100), yval=rnorm(100))
ggplot(df, aes(x=xval, y=yval)) +
geom_point(size=5, shape=21, colour="black", fill="white", alpha=.5)
Attached are a scatterplot (generated by the code below) and a zoomed-in view of a PDF with these shapes. In the zoomed-in view, you can see the edge of the white circle underneath the green ring.
df <- data.frame(xval=rnorm(100), yval=rnorm(100))
ggplot(df, aes(x=xval, y=yval)) +
geom_point(size=5, shape=21, colour="black", fill="white", alpha=.5)
baptiste auguie
Jun 5, 2009, 4:05:53 AM6/5/09
to Winston Chang, ggplot2
>
> point_fill_zoom.png
>
> >
Hi,
I'm not sure I'm following you --- is it the same effect as in the
example attached (the border of the point is partially covering the
interior of the disc). It seems to me that it's a characteristic of the
point symbols to have the line expand symmetrically inside and outside
when increasing the linewidth, and presumably the border is drawn on top
of the interior region at the engine level. But perhaps I misunderstood
your query?
# code
library(ggextra)
qplot(0, 0, geom="blank")+
geom_point2(size=50, shape=21, fill=alpha("grey", 0.5), col=alpha("red",
0.2), lex=20) +
theme_minimal()
Best,
baptiste
hadley wickham
Jun 5, 2009, 9:15:14 AM6/5/09
to baptiste auguie, Winston Chang, ggplot2
> I'm not sure I'm following you --- is it the same effect as in the
> example attached (the border of the point is partially covering the
> interior of the disc). It seems to me that it's a characteristic of the
> point symbols to have the line expand symmetrically inside and outside
> when increasing the linewidth, and presumably the border is drawn on top
> of the interior region at the engine level. But perhaps I misunderstood
> your query?
> example attached (the border of the point is partially covering the
> interior of the disc). It seems to me that it's a characteristic of the
> point symbols to have the line expand symmetrically inside and outside
> when increasing the linewidth, and presumably the border is drawn on top
> of the interior region at the engine level. But perhaps I misunderstood
> your query?
Winston was using the alpha _aesthetic_, and he's right in expecting
that it should affect the fill colour as well. I've fixed it in the
development version. Unfortunately there's not much I can do about
the slightly strange appearance that results.
Hadley
baptiste auguie
Jun 5, 2009, 10:35:34 AM6/5/09
to ggplot2
Sorry I misinterpreted the example you provided. The good news is, your
issue can be addressed, while the one I had made up out of the blue
would be more problematic!
Best,
baptiste
>
> point_fill_zoom.png
>
> >
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