The result of this function can be added to an assemble using + in the same
way as plot_layout(), but unlike plot_layout() it will only have an
effect on the top level plot. As the name suggests it controls different
aspects of the annotation of the final plot, such as titles and tags.
plot_annotation(title = NULL, subtitle = NULL, caption = NULL,
tag_levels = NULL, tag_prefix = NULL, tag_suffix = NULL,
tag_sep = NULL, theme = NULL)Text strings to use for the various plot annotations.
A character vector defining the enumeration format to use
at each level. Possible values are 'a' for lowercase letters, 'A' for
uppercase letters, '1' for numbers, 'i' for lowercase Roman numerals, and
'I' for uppercase Roman numerals.
Strings that should appear before or after the tag.
A separator between different tag levels
A ggplot theme specification to use for the plot. Only elements related to the titles as well as plot margin and background is used.
A plot_annotation object
Tagging of subplots is done automatically and following the order of the
plots as they are added. When the plot contains nested layouts the
tag_level argument in the nested plot_layout will define whether
enumeration should continue as usual or add a new level. The format of the
levels are defined with tag_levels argument in plot_annotation