ggplot geom_text font size control

Question

I tried to change the font to 10 for the labels of my bar plot in ggplot2 by doing something like this:

ggplot(data=file,aes(x=V1,y=V3,fill=V2)) +     geom_bar(stat="identity",position="dodge",colour="white") +      geom_text(aes(label=V2),position=position_dodge(width=0.9),                                                  hjust=1.5,colour="white") +     theme_bw()+theme(element_text(size=10))  ggsave(filename="barplot.pdf",width=4,height=4) 

but the resulting image has super big font size for the bar plot labels.

Then I thought of modifying in geom_text() with this:

geom_text(size=10,aes(label=V2),position=position_dodge(width=0.9),                                                    hjust=1.5,colour="white") 

The label font is even bigger...

I can change the size within geom_text to something like 3 and now it looks like font 10, similar to the axis labels.

I'm wondering what's going on? Does theme(text=element_text(size=10)) doesn't apply to labels?

And why size of 10 in geom_text() is different from that in theme(text=element_text()) ?

Answer 1

Here are a few options for changing text / label sizes

library(ggplot2)  # Example data using mtcars  a <- aggregate(mpg ~ vs + am , mtcars, function(i) round(mean(i)))  p <- ggplot(mtcars, aes(factor(vs), y=mpg, fill=factor(am))) +              geom_bar(stat="identity",position="dodge") +              geom_text(data = a, aes(label = mpg),                              position = position_dodge(width=0.9),  size=20) 

The size in the geom_text changes the size of the geom_text labels.

p <- p + theme(axis.text = element_text(size = 15)) # changes axis labels  p <- p + theme(axis.title = element_text(size = 25)) # change axis titles  p <- p + theme(text = element_text(size = 10)) # this will change all text size                                                               # (except geom_text) 

For this And why size of 10 in geom_text() is different from that in theme(text=element_text()) ?

Yes, they are different. I did a quick manual check and they appear to be in the ratio of ~ (14/5) for geom_text sizes to theme sizes.

So a horrible fix for uniform sizes is to scale by this ratio

geom.text.size = 7 theme.size = (14/5) * geom.text.size  ggplot(mtcars, aes(factor(vs), y=mpg, fill=factor(am))) +    geom_bar(stat="identity",position="dodge") +    geom_text(data = a, aes(label = mpg),              position = position_dodge(width=0.9),  size=geom.text.size) +    theme(axis.text = element_text(size = theme.size, colour="black"))  

This of course doesn't explain why? and is a pita (and i assume there is a more sensible way to do this)