On 17 Nov 2008, at 13:00, hadley wickham wrote:
Hi Dave,
On Mon, Nov 17, 2008 at 6:35 AM, Dave Murray-Rust
<[EMAIL PROTECTED]> wrote:
I'm trying to plot multiple lines using different colours/symbols to
distinguish them. If I try to plot more than 6 lines, I get an error:
ggplot( dat, aes(x=time,y=value,group=variable,shape=variable) ) +
geom_line()
Error: scale_shape can deal with a maximum of 6 discrete values,
but you
have 9. See ?scale_manual for a possible alternative
I find this slightly confusing, as there are ~25 symbols listed for
use.
(I'm using ggplot2 0.7, on OSX, R 2.7.2)
But distinguishing between more than 6 of is very difficult!
Absolutely! But it's easier than between different colours of line,
especially given low-quality printer output...
I guess the "correct" answer is that if you're trying to plot more
than 6 lines on the graph, you need to rethink the graph.
Ideally, I'd like to use a combination of colours and symbols (e.g. 5
colours and 4 symbols -> 20 unique possibilities) or even colours,
symbols
and linetypes - is there a way to do this in ggplot2?
Unfortunately not - this type of combined scale is on my to do list,
but I haven't got around to it yet. Here's a work around:
df <- data.frame(a = 1:20, b = 1:20, c = letters[1:20])
qplot(a, b, data = df, colour = c)
df$d <- factor(rep(1:5, each = 4))
df$e <- factor(rep(1:4, by = 5))
qplot(a, b, data = df, colour = d, shape = e)
Ah, thanks for that; I'd been trying something similar, with slightly
limited success.
Generally, I'd wouldn't advise splitting up a single variable across
two aesthetics like this: perceptually I don't think its a great idea.
I agree, that is quite confusing - a combined scale would definitely
be more clear.
Thanks for the info!
Cheers,
dave
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