ggplot2: Adjust the symbol size in legends

Question

How should I change the size of symbols in legends? I checked the document of theme but found no answer.

Here is an example:

library(ggplot2);library(grid) set.seed(1000) x <- 1:6 mu <- sin(x) observed <- mu + rnorm(length(x), 0, 0.5*sd(mu)) data <- data.frame(   t=rep(x, 2),    value=c(mu, observed) - min(mu, observed) + 0.5,    class = rep(c("mu", "observed"), each=length(x))) mu <- data$value[1:length(x)] observed <- data$value[1:length(x) + length(x)] mu.min <- mu - 3 * 0.5 * sd(mu) mu.max <- mu + 3 * 0.5 * sd(mu) g <- ggplot(data=data) g <- g + geom_point(aes(x=value, y=t, shape=class, size=24)) + scale_size(guide="none") g <- g + scale_shape(name="", labels=expression(paste(S[u](t), ", the observation at time ", t), paste(mu[u](t), ", the mean of ", tilde(S)[u](t), "          "))) stat_function.color <- gray(0.5) g <- g + geom_segment(aes(y=1:6, yend=1:6, x=mu.min, xend=mu.max, linetype="2", alpha = 1), color=stat_function.color) + scale_alpha(guide="none") + scale_linetype(name= "", labels=expression(paste("probability density function (pdf) of ", tilde(S)[u], " at time ", t))) for(i in 1:length(x)) {   g <- g + stat_function(fun=function(x, i) {     ifelse( x <= mu.max[i] & x >= mu.min[i], dnorm(x, mu[i], sd(mu)) + i, NA)     }, color=stat_function.color, args=list(i=i)) } background.color <- gray(0.75) g <- g + theme(   axis.text=element_blank(),   title=element_text(size=rel(1.5)),   legend.text=element_text(size=rel(1.5)),   legend.position="top",   legend.direction="vertical", #   legend.key.size = unit(2, "cm"),   panel.background=element_rect(fill=background.color),    panel.grid.major=element_line(color=background.color),   panel.grid.minor=element_line(color=background.color)   ) + coord_flip() plot(g) 

Answer 1

You should use:

theme(legend.key.size = unit(3,"line"))