n_pages: Determine the number of pages in a paginated facet plot
Description
This is a simple helper that returns the number of pages it takes to plot all
panels when using facet_wrap_paginate and
facet_grid_paginate. It partially builds the plot so depending
on the complexity of your plot it might take some time to calculate...
Usage
n_pages(plot)
Arguments
plot
A ggplot object using either facet_wrap_paginate or
facet_grid_paginate
Value
If the plot uses using either facet_wrap_paginate or
facet_grid_paginate it returns the total number of pages. Otherwise it
returns NULL