How can I make a legend in ggplot2 with one input point and one line?

Question

I am making a graph in ggplot2 consisting of a set of data points plotted as points, with the lines predicted by the installed overlay model. The general idea of ​​the chart looks something like this:

names <- c(1,1,1,2,2,2,3,3,3) xvals <- c(1:9) yvals <- c(1,2,3,10,11,12,15,16,17) pvals <- c(1.1,2.1,3.1,11,12,13,14,15,16) ex_data <- data.frame(names,xvals,yvals,pvals) ex_data$names <- factor(ex_data$names) graph <- ggplot(data=ex_data, aes(x=xvals, y=yvals, color=names)) print(graph + geom_point() + geom_line(aes(x=xvals, y=pvals))) 

As you can see, both lines and dots are colored by a categorical variable (in this case, “names”). I would like the legend to contain 2 entries: a dot labeled “data” and a string labeled “Fitted” (to indicate that the dots are real data, and the lines fit). However, I cannot get this to work. The (Awesome) guide here is great for formatting, but doesn't deal with the actual recordings, while I tried the technique here to no avail, i.e.

 print(graph + scale_colour_manual("", values=c("green", "blue", "red")) + scale_shape_manual("", values=c(19,NA,NA)) + scale_linetype_manual("",values=c(0,1,1))) 

The main problem is that in my actual data there are> 200 different categories for "names", while I only need 2 entries mentioned above in the legend. Doing this with my actual data simply creates a meaningless legend that runs away from the page because the legend is trying to be the key to the colors (which I have too many).

I would be grateful for any help!

Answer 1

I think this is close to what you want:

 ggplot(ex_data, aes(x=xvals, group=names)) + geom_point(aes(y=yvals, shape='data', linetype='data')) + geom_line(aes(y=pvals, shape='fitted', linetype='fitted')) + scale_shape_manual('', values=c(19, NA)) + scale_linetype_manual('', values=c(0, 1)) 

The idea is that you specify two aesthetics ( linetype and shape ) for both lines and points, although it does not make sense, for example, so that the point has linetype aesthetics. Then you manually match these “meaningless” aesthetics with “zero” values ​​( NA and 0 in this case) using a manual scale.

Answer 2

This has already been answered, but based on the feedback, I got another question ( How can I fix this strange behavior of the legend in ggplot2? ) This setting can be useful to others and can save you headaches (sorry, could not comment on the previous answer ):

 ggplot(ex_data, aes(x=xvals, group=names)) + geom_point(aes(y=yvals, shape='data', linetype='data')) + geom_line(aes(y=pvals, shape='fitted', linetype='fitted')) + scale_shape_manual('', values=c('data'=19, 'fitted'=NA)) + scale_linetype_manual('', values=c('data'=0, 'fitted'=1))