On 4/23/2012 9:24 AM, Matthias Rieber wrote:
Hello,
I've some problem with the ggplot2. Here's a small example:
--8<--
library(ggplot2)
molten<- data.frame(date=c('01','01','01','01',
'02','02','02','02'),
channel=c('red','red','blue','blue',
'red','red','blue','blue'),
product=c('product1','product2',
'product1','product2',
'product1','product2',
'product1','product2'),
value=c(1,1,1,1,
1,1,1,1))
str(molten)
molten
ggplot(molten, aes(date, weight = value, fill = channel)) +
geom_bar(colour = I('black')) + facet_grid(product ~ .)
-->8--
This gives the expected result (at least I expect this, see attachment
case1). When I change molten to:
molten<- data.frame(date=c('01','01','01','01',
'02','02','02','02'),
channel=c('red','red','blue','blue',
'red','red','blue','blue'),
product=c('product1','product2',
'product1','product2',
'product1','product1',
'product1','product2'),
value=c(1,1,1,1,
1,1,1,1))
I get a strange result(see case2). I expect that for date=02 and
product=product1 the bar should show 2 'red', but it's just 1. So the
total sum is 7 instead of 8.
When I change molten again:
molten<- data.frame(date=c('01','01','01','01',
'02','02','02','02'),
channel=c('red','red','blue','blue',
'red','red','blue','blue'),
product=c('product1','product2',
'product1','product2',
'product1','product1',
'product1','product2'),
value=c(1,1,1,1,
1,2,1,1))
I get the expected result, where the bar show 3 'red' and the total sum
is 9.
Is it wrong to use geom_bar with that kind of data? I could avoid this
issue when I cast the data.frame, but I like to avoid that solution.
There is nothing wrong with using bars with this sort of data. There is
a bug in the faceting code of 0.9.0 that will be fixed in 0.9.1 (see
https://github.com/hadley/ggplot2/issues/443 ) which caused duplicate
rows of data to be dropped when there was faceting. That is what you are
seeing in the second example; row 6 is identical to row 7 and is dropped
before plotting. One easy workaround until 0.9.1 comes out is to add
unique column to the data that is otherwise ignored:
molten <- data.frame(date=c('01','01','01','01',
'02','02','02','02'),
channel=c('red','red','blue','blue',
'red','red','blue','blue'),
product=c('product1','product2',
'product1','product2',
'product1','product1',
'product1','product2'),
value=c(1,1,1,1,
1,1,1,1),
dummy=1:8)
Matthias
--
Brian S. Diggs, PhD
Senior Research Associate, Department of Surgery
Oregon Health & Science University
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