Fine grained control over X and Y ticks.

[v0dro]

What is the best way to gain control over X and Y ticks? I read the PlotAxes class in the Python wrapper but could not find anything concrete. I'm mainly looking for a way to supply tick labels and their various properties like text rotation, color, placement on the Axis etc.

[cfelder]

In order to have fine grained control of the labels you can supply callback functions for the x and y axis which will be called for every tick label.

You can either use gr.axeslbl which has basically the same signature as gr.axes but adds two function pointers fpx and fpy or if you want to use the PlotAxes class you can use setXtickCallback and setYtickCallback to point to the corresponding functions.

The callback functions should have 4 parameters: x, y, svalue, value where::

• x is the normalised device coordinate of the label in x direction
• y is the normalised device coordinate of the label in y direction
• svalue is the internal string representation respectively the text usually drawn by gr at x, y
• value is the floating point representation of the label drawn at x, y

Within the callback function you can simply use gr drawing primitives to draw the text, e.g: the following code which prints a formatted date and time string on the x axis and rotates the labels:

        gr.setcharup(-1. if self.leftTurnedLegend else 1., 1.)
        gr.settextalign(gr.TEXT_HALIGN_RIGHT, gr.TEXT_VALIGN_TOP)
        dx = .015
        timeVal = time.localtime(value)
        gr.text(x + dx, y, time.strftime(DATEFMT, timeVal))
        gr.text(x - dx , y, time.strftime(TIMEFMT, timeVal))
        gr.setcharup(0., 1.)  # restore default charup vector

[v0dro]

Ah. Would be great to see this documented. I can send a PR if you're OK with it?

[jheinen]

Feel free to submit a PR 👍

[v0dro]

On it :)

[cfelder]

@v0dro great. Here is also some example output:

[v0dro]

@cfelder is there a way to set the co-ordinates of each tick and the label without relying on the parameters passed to axeslbl? For example something like pyplot.xticks.