20.2 Themes

How about creating new theme elements?

The base is theme is theme_grey(), then here is an example of the modification made on theme_bw() to obtain theme_minimal(). The theme_* is the easiest part of a plot to be modified.

Use the print() function on a theme_<…> to see its specifications, the %+replace% operator shows where the substitutions have taken place.

print(theme_grey)
print(theme_minimal) and %+replace% operator

print(theme_bw)

function (base_size = 11, base_family = "", base_line_size = base_size/22, 
    base_rect_size = base_size/22) 
{
    theme_grey(base_size = base_size, base_family = base_family, 
        base_line_size = base_line_size, base_rect_size = base_rect_size) %+replace% 
        theme(panel.background = element_rect(fill = "white", 
            colour = NA), panel.border = element_rect(fill = NA, 
            colour = "grey20"), panel.grid = element_line(colour = "grey92"), 
            panel.grid.minor = element_line(linewidth = rel(0.5)), 
            strip.background = element_rect(fill = "grey85", 
                colour = "grey20"), complete = TRUE)
}
<bytecode: 0x55a4fa5f12e0>
<environment: namespace:ggplot2>

print(theme_minimal)

function (base_size = 11, base_family = "", base_line_size = base_size/22, 
    base_rect_size = base_size/22) 
{
    theme_bw(base_size = base_size, base_family = base_family, 
        base_line_size = base_line_size, base_rect_size = base_rect_size) %+replace% 
        theme(axis.ticks = element_blank(), legend.background = element_blank(), 
            legend.key = element_blank(), panel.background = element_blank(), 
            panel.border = element_blank(), strip.background = element_blank(), 
            plot.background = element_blank(), complete = TRUE)
}
<bytecode: 0x55a5030b5090>
<environment: namespace:ggplot2>

While if we call the function: print(theme_minimal()), we can see all the options set available. In general, if you want to make a modification to an existing theme, the general approach is to simply use the theme() function while setting complete = TRUE.

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