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jwbargsten/density2d_map.R

Created July 18, 2013 15:03
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plot pretty 2d density map with ggplot2
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density2d_map.R
library(ggplot2)
library(MASS)
## generate some random data
data <- data.frame(a=abs(rnorm(1000, mean=0.5)), b=abs(rnorm(1000, mean=0.5)))
data$a <- data$a / max(data$a)
data$b <- data$b / max(data$b)
## layout settings for ggplot
t2 <- theme(
axis.line = element_line(colour = "black"),
axis.text = element_text(colour = "black"),
axis.ticks = element_line(colour = "black"),
panel.grid.major.x = element_blank(),
panel.grid.minor.x = element_blank(),
panel.grid.major.y = element_blank(),
panel.grid.minor.y = element_blank(),
panel.border = element_blank(),
panel.background = element_blank()
)
## generate the "z" coordinate (density) just for the correct midpoint in the color gradient
z <- kde2d(data$a, data$b)
g <- ggplot(data, aes(x=a, y=b)) +
stat_density2d(aes(fill=..density..), geom="tile", contour=FALSE) +
scale_fill_gradient2(low="#44aa00", mid="#ffcc00", high="#502d16", midpoint=mean(range(z$z))) +
## limit scale ( density is calculated on the limited scale, all other points are removed from calculation)
#xlim(0,1) +
#ylim(0,1) +
## limit view area ( density is calcluated on all points, no points removed )
coord_cartesian(xlim = c(0, 1), ylim=c(0,1)) +
xlab("x method") +
ylab("y method") +
## add points to the density map (comment it if not desired)
geom_point(size=0.6, colour="white",shape=1, alpha=0.2) +
## make a line from (0,0) - (1,1)
#geom_segment(aes(x=0, y=0, xend=1, yend=1)) +
## or just create a abline with slope 1 and intercept 0
geom_abline() +
t2
pdf("density.pdf", width=0.25*6+6, height=6)
g
dev.off()
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