In case you were struggling to change linetypes, the following answer should be helpful. (This is an addition to the solution by Andy W.)
We will try to extend the learned pattern:
cols <- c("LINE1"="#f04546","LINE2"="#3591d1","BAR"="#62c76b")
line_types <- c("LINE1"=1,"LINE2"=3)
ggplot(data=data,aes(x=a)) +
geom_bar(stat="identity", aes(y=h,fill = "BAR"))+ #green
geom_line(aes(y=b,group=1, colour="LINE1", linetype="LINE1"),size=0.5) + #red
geom_point(aes(y=b, colour="LINE1", fill="LINE1"),size=2) + #red
geom_line(aes(y=c,group=1,colour="LINE2", linetype="LINE2"),size=0.5) + #blue
geom_point(aes(y=c,colour="LINE2", fill="LINE2"),size=2) + #blue
scale_colour_manual(name="Error Bars",values=cols,
guide = guide_legend(override.aes=aes(fill=NA))) +
scale_linetype_manual(values=line_types)+
scale_fill_manual(name="Bar",values=cols, guide="none") +
ylab("Symptom severity") + xlab("PHQ-9 symptoms") +
ylim(0,1.6) +
theme_bw() +
theme(axis.title.x = element_text(size = 15, vjust=-.2)) +
theme(axis.title.y = element_text(size = 15, vjust=0.3))
However, what we get is the following result:
The problem is that the linetype is not merged in the main legend.
Note that we did not give any name to the method scale_linetype_manual.
The trick which works here is to give it the same name as what you used for naming scale_colour_manual.
More specifically, if we change the corresponding line to the following we get the desired result:
scale_linetype_manual(name="Error Bars",values=line_types)
Now, it is easy to change the size of the line with the same idea.
Note that the geom_bar has not colour property anymore. (I did not try to fix this issue.) Also, adding geom_errorbar with colour attribute spoils the result. It would be great if somebody can come up with a better solution which resolves these two issues as well.