In R graphics, what is the different between plotting characters (pch) 16 and 19?

Question

I can't find any documentation other than mentions of "filled" vs "solid".

library(graphics)
plot.new()
points(.48, .5, pch=19)
points(.52, .5, pch=16)

Edit: Winston Chang's explanation answeres my question pretty thoroughly https://github.com/hadley/ggplot2/issues/1757#issuecomment-247804365

Answer 1

This may help:

Values of pch are stored internally as integers. The interpretation is

NA_integer_: no symbol.

0:18: S-compatible vector symbols.

19:25: further R vector symbols.

26:31: unused (and ignored).

32:127: ASCII characters.

128:255 native characters only in a single-byte locale and for the symbol font. (128:159 are only used on Windows.)

-32 ... Unicode code point (where supported).

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