How to scale the size of line and point separately in ggplot2

The two ways I can think of are 1) combining two legend grobs or 2) hacking another legend aesthetic. Both of these were mentioned by @Mike Wise in the comments above.

Approach #1: combining 2 separate legends in the same plot using grobs.

I used code from this answer to grab the legend. Baptiste's arrangeGrob vignette is a useful reference.

library(grid); library(gridExtra)#Function to extract legend grobg_legend <- function(a.gplot){  tmp <- ggplot_gtable(ggplot_build(a.gplot))  leg <- which(sapply(tmp$grobs, function(x) x$name) == "guide-box")  legend <- tmp$grobs[[leg]]  legend}#Create plotsp1 <- ggplot()+  geom_point(aes(x,y,size=z),data=d1) + scale_size(name = "point")p2 <- ggplot()+  geom_line(aes(x,y,size=z),data=d2) + scale_size(name = "line")p3 <- ggplot()+  geom_line(aes(x,y,size=z),data=d2) +         geom_point(aes(x,y, size=z * 100),data=d1)  # Combined plotlegend1 <- g_legend(p1)legend2 <- g_legend(p2)legend.width <- sum(legend2$width)  gplot <- grid.arrange(p3 +theme(legend.position = "none"), legend1, legend2,             ncol = 2, nrow = 2,             layout_matrix = rbind(c(1,2 ),                                     c(1,3 )),              widths = unit.c(unit(1, "npc") - legend.width, legend.width))grid.draw(gplot)

Note for printing: use arrangeGrob() instead of grid.arrange(). I had to use png; grid.draw; dev.off to save the (arrangeGrob) plot.

Approach #2: hacking another aesthetic legend.

MilanoR has a great post on this, focusing on colour instead of size.More SO examples: 1) discrete colour and 2) colour gradient.

#Create discrete levels for point sizes (because points will be mapped to fill)d1$z.bin <- findInterval(d1$z, c(0,2,4,6,8,10), all.inside= TRUE)  #Create bins#Scale the points to the same size as the lines (points * 100).  #Map points to a dummy aesthetic (fill)#Hack the fill properties.ggplot()+  geom_line(aes(x,y,size=z),data=d2) +   geom_point(aes(x,y, size=z * 100, fill = as.character(z.bin)),data=d1) +  scale_size("line", range = c(1,5)) +   scale_fill_manual("points", values = rep(1, 10) ,                     guide = guide_legend(override.aes =                               list(colour = "black",                               size = sort(unique(d1$z.bin)) )))

I'm a noob in programming, but you could try this methode. As you see, my code uses points and paths. I define a vector of the length of number of paths. My lines have the size 1. Then I add the sizes of my points at the back of that vector.

size_vec<-c(rep(1, length(unique(Data$Satellite))), 1.4, 4.6, 4.2, 5.5)plot <- ggplot(data) +geom_point(aes(x = x_cor, y = y_cor, shape=Type, size=Type)) +geom_path(aes(x = x_cor, y = y_cor, group = Tour, size=factor(Satellite))) +scale_size_manual(values = size_vec, guide ='none')