I am generating some maps and animations with tmap, using tm_facets. The default style shows rather ugly grey headers for each small map. How can I change the style of the header (position, font size/family, background colour)?
tm_shape(Europe) + tm_polygons("well_being", title="Well-Being Index") + tm_facets("part", free.coords=FALSE) + tm_style_grey()
Similar code snippets are available in the R Vignette.