Richard.Cotton wrote:
The rectangles being drawn extend higher than the top of the panel.
(Your y
axis ranges from 0 to 50, but the bars go up to 100.)
Thankyou - I can also make the bars on the lower panels vanish by
tinkering with ylim.
In the top row of plots, depending upon the shape of your device
window, the
bars can extend beyond the range of the device window. For some
reason,
(take a look in panel.rect), when you specify alpha less than 1, this
prevents the bar being drawn.
The problem lies deeper. I can demonstrate the same effect with raw grid
calls (but cannot find a way into "grid.draw" to see what is going on):
cols <- rainbow(2,alpha=0.5)
library(grid)
grid.newpage()
pushViewport(plotViewport(c(5,4,2,2)))
# draw viewport limits:
grid.rect()
# VISIBLE: small projection outside viewport, transparent fill and edge
grid.rect(gp=gpar(fill=cols[2],col=cols[1]),height=unit(1.1,"npc"),width
=unit(0.18,"npc"),x=0.1)
# VISIBLE: small projection outside viewport, standard colours fill and
edge
grid.rect(gp=gpar(fill=2,col=3),height=unit(1.1,"npc"),width=unit(0.18,"
npc"),x=0.3)
# INVISIBLE: larger projection outside viewport, transparent colours
fill and edge
grid.rect(gp=gpar(fill=cols[2],col=cols[1]),height=unit(1.5,"npc"),width
=unit(0.18,"npc"),x=0.5)
# VISIBLE: larger projection outside viewport, standard colours fill and
edge
grid.rect(gp=gpar(fill=2,col=3),height=unit(1.5,"npc"),width=unit(0.18,"
npc"),x=0.7)
# MIXED: larger projection outside viewport, standard colour edge
visible, transparent fill not
grid.rect(gp=gpar(fill=cols[2],col=3),height=unit(1.5,"npc"),width=unit(
0.18,"npc"),x=0.9)
I can also show the same effect using standard graphics calls:
par(xpd=NA)
plot(c(1,2))
rect(1.01,1,1.19,2.2,border=cols[1],col=cols[2])
rect(1.21,1,1.39,2.2,border=3,col=2)
rect(1.41,1,1.59,4,border=cols[1],col=cols[2])
rect(1.61,1,1.79,4,border=3,col=2)
rect(1.81,1,1.99,4,border=3,col=cols[2])
Both of these examples have missing alpha transparency colours under
Windows but produce the expected filled rectangles under Linux.
You need to add type="count" to the call to histogram, or rescale the
bar
heights.
My post was a rather simplified example - I am actually trying to make
visible a "small" distribution on the skirt of a large one, which means
that scaling the bar heights is not sufficient. I have worked around the
problem by modifying panel.histogram to _clip_ the bar heights.
Keith
Keith Ponting
Aurix Ltd, Malvern WR14 3SZ UK
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