Fine control of axis types in axes/xaxt/yaxt

[zeileis]

As discussed in #182 I have tried to implement character specifications of different axis types. The docs of the relevant arguments in tinyplot.default now say:

• axes: logical or character. Should axes be drawn (TRUE or FALSE)? Or alternatively what type of axes should be drawn: "standard" (with axis, ticks, and labels; equivalent to TRUE), "none" (no axes; equivalent to FALSE), "ticks" (only ticks and labels without axis line), "labels" (only labels without ticks and axis line), "axis" (only axis line and labels but no ticks). To control this separately for the two axes, use the character specifications for xaxt and/or yaxt.
• xaxt, yaxt: character specifying the type of x-axis and y-axis, respectively. See axes for the possible values.

Illustration:

library("tinyplot")
x <- 0:100/10
y <- sin(x)
tinyplot(y ~ x, type = "l", lwd = 2, col = "steelblue", grid = TRUE, main = 'default')
tinyplot(y ~ x, type = "l", lwd = 2, col = "steelblue", grid = TRUE, main = 'axes = "ticks"', axes = "ticks")
tinyplot(y ~ x, type = "l", lwd = 2, col = "steelblue", grid = TRUE, main = 'axes = "labels"', axes = "labels")
tinyplot(y ~ x, type = "l", lwd = 2, col = "steelblue", grid = TRUE, main = 'axes = "axis"', axes = "axis")
tinyplot(y ~ x, type = "l", lwd = 2, col = "steelblue", grid = TRUE, main = 'xaxt = "ticks", yaxt = "labels"', xaxt = "ticks", yaxt = "labels")
tinyplot(y ~ x, type = "l", lwd = 2, col = "steelblue", grid = TRUE, main = 'axes = "none", yaxt = "standard"', axes = "none", yaxt = "standard")

Note that the plot in the bottom left panel is maybe unexpected. The reason is that frame.plot is solely selected based on axes (which is TRUE here) and not based on xaxt/yaxt. One could consider changing that but I felt that the selection of the defaults is already involved enough for a first proposal.

Feel free to make any changes or discard the PR if it's not useful (in this way).

[zeileis]

Unrelated bonus question which I noticed when preparing the example enough. Is it intentional that for the x and y sinus example from above, the following plots differ? The former is just black while the latter gets a continuous palette.

tinyplot(y ~ x)
tinyplot(sin(x) ~ x)

[grantmcdermott]

This looks great, thanks @zeileis. I'm out with the family atm but will be and to review properly when I'm back home.

[zeileis]

While mowing the lawn I thought that it would be better to handle all defaults of axes, xaxt, yaxt, and frame.plot early on in tinyplot.default. This means that the could is in a different place than the actual drawing of the axes but the defaults could be handled in a cleaner and more intelligible way. The default of frame.plot is now NULL and then we can do: https://github.com/grantmcdermott/tinyplot/blob/axis-type/R/tinyplot.R#L532-L545

This still produces the same plots as above except for the bottom left panel which is now drawn without a frame.

[grantmcdermott]

@zeileis This is great. Your plot examples look very slick!

My only minor request is to make tinyAxis() its own unexported function (as you suggested).

[zeileis]

Just in case tinyAxis() also gets called elsewhere in the future, I improved the implementation and made sure that the arguments enforced through the type do not conflict with the ... arguments.

[grantmcdermott]

Closes #182 .

[grantmcdermott]

Thanks @zeileis!