ggplot2: example codes for matrix-like legend guide

example codes

p <- qplot(1:20, 1:20, col=letters[1:20])
p + guides(col=guide_legend(nrow=8))
p + guides(col=guide_legend(ncol=8))
p + guides(col=guide_legend(nrow=8, byrow=T))
p + guides(col=guide_legend(ncol=8, byrow=T))

# output plots: http://yfrog.com/klhjpwp
# how to embed images in gist...?

how to install dev version ggplot2

# you can install very very easily the develop version of ggplot2 on github thanks to Hadley's devtools package.

install.packages('devtools')
install.packages(c("RColorBrewer", "stringr", "dichromat", "munsell", "plyr", "colorspace")) # probably windows only

library(devtools)
dev_mode(TRUE)

install_github("scales")
install_github("ggplot2", "kohske", "feature/new-guides-with-gtable")

library(ggplot2)

The "cutting-edge" version seemed to fix the problem.

Two small(ish) problems with the ways the legend is now constructed with guides():

It seems that the legend labels are now centered rather than left-justified as they were before. I wonder if there is a parameter to put the labels back to left justification.

Also, when I set the legend.position to "bottom", the legend ends up in the bottom right hand corner of the plot window, rather than at the bottom and centered as it is in the official version.

My code is as follows:

ggplot(Dataset) +
my.theme(base_size = textsize) +
stat_density(aes(x = theAnswer, colour = theGroup, order = as.factor(theGroup)), size = 1, adjust = smooth, geom = "path", position = "identity") +
#facet_wrap(~question) +
coord_cartesian(xlim = c(0.5,5.5)) +
scale_x_continuous(breaks = c(1,2,3,4,5),
labels = answerLabels[(answer_5-4):(answer_5)]) +
scale_y_continuous(breaks = NA) +
labs(x = NULL, y = NULL, colour = "") +
opts(legend.position = "bottom",
legend.direction = "horizontal",
legend.key.size = unit((textsize/13), "lines"),
panel.background = theme_rect(fill = "grey14", colour = "grey14"),
plot.background = theme_rect(colour = "grey14"),
panel.border = theme_rect(fill = NA, colour = "grey90", size = 1.25),
plot.margin = unit(c(0, 7, 0, 5.5), "lines")) +
scale_colour_manual(breaks = legendOrder, values = color) +
guides(col=guide_legend(ncol=3))

Thanks again!

could you please provide a reproducible example?
?guide_legend will show you help page.

how can i set the legend row into one?

@kohske