theme_update(text) fails due to NULL values

[oneillkza]

It's possible, using theme(), to set individual font elements inline with plotting, eg (adapted from ggplot documentation example):

df <- data.frame(gp = factor(rep(letters[1:3], each = 10)), y = rnorm(30))
ggplot(df, aes(x = gp, y = y)) + 
    geom_point() +
    theme(text=element_text(size=16))

However, when using theme_update to try to set this globally, it complains about NULL values in the text element.

theme_update(text=element_text(size=16))
ggplot(df, aes(x = gp, y = y)) + 
    geom_point()

results in

Error in FUN(X[[i]], ...) : 
  Theme element 'text' has NULL property: family, face, colour, hjust, vjust, angle, lineheight, margin, debug

I don't know if this is intended, but it seems strange that the behaviour of theme() and update_theme() is different, and it's frustrating that it isn't possible to set font size globally.

(This is with ggplot2_2.0.0.)

[wmayner]

I'm having the same problem, though I'm updating the theme manually with

my.theme = theme_grey() + theme(text=element_text(family='Roboto', size=30))

As with OP, the same modification on a ggplot object works fine; it's only when trying to modify the default theme that this error is raised.

[oneillkza]

Interestingly, as a work-around, the following does work:

theme_set(theme_bw(base_size = 16))
ggplot(df, aes(x = gp, y = y)) + 
    geom_point()

[hadley]

The base theme settings which are inherited by other settings need to be fully specified. Otherwise nothing gets inherited.

[oneillkza]

I see. So the solution for actually updating a single element of an element of a theme is something like:

theme_update(text=(theme_grey()+theme(text = element_text(family = "Times")))$text )

That's pretty ugly; I'd expect theme_update to pull the base theme settings from the theme being updated, rather than requiring them to all be specified. It's your package, though.

[hadley]

@oneillkza there's probably a better way to do it than that, but I hardly ever use themes so I'm the wrong person to ask.

[oneillkza]

Thanks Hadley, that's understandable.

Hmm ... looking at the actual definition for theme_update(), it seems like the issue is that it uses %+replace% instead of +.

theme_update <- function(...) {
# Make a call to theme, then add to theme
theme_set(theme_get() %+replace% theme(...))
}

So for now the better way to update individual elements in a theme is to bypass theme_update and just to use theme_set directly:

theme_set(theme_get() + theme(text=element_text(size=16)))
theme_get()$text

It'd be nice to have an update function that uses +, but I'll create a new issue articulating this, since this is becoming more of a feature request.

[oneillkza]

Or, rather, I'll make a pull request ;)

[eejd]

@oneillkza , Can't you just use the theme() for your needs?

[oneillkza]

@eejd In a round-about way (see conversation above), but anyway this problem was solved in #1519 , so I can just use the current version of the package ;)