*From*: John Denker <jsd av8n com>*To*: gnumeric-list gnome org*Subject*: Re: manual ticks of an axis*Date*: Tue, 25 Nov 2014 07:36:37 -0700

On 11/25/2014 05:15 AM, Jean Brefort wrote:

There is already an enhancement request: https://bugzilla.gnome.org/show_bug.cgi?id=600482. I'm unsure about random ticks. I'd like a significant use case for them before trying to implement them.

Could we please call them /manual/ ticks or /arbitrary/ ticks rather than "random" ticks? Also note that it is the ticks and labels that are important; the "axis" itself becomes a nuisance and a source of confusion as soon as you try to do anything nontrivial, such as a spacetime diagram or ternary phase diagram; for details see https://www.av8n.com/physics/axes.htm ============= The discussion of use cases starts with the observation that a gnumeric XY plot offers two "types" of axes: linear and logarithmic. These must be considered two special cases in a vast universe of possibilities. It would be nice to handle the general case. Case 1: Arrhenius law: rate proportional to exp(1/T). To represent this as a straight line, it is necessary to plot log(rate) versus 1/T. It would be nice to have ticks labeled in terms of T, not 1/T: position label 1/4 T=4 1/2 T=2 2/3 T=1.5 1 T=1 Case 2: Ohm's law. Current as a function of inverse resistance at constant voltage. Similar to case 1, without the exponential. Case 3: The resistance of a carbon-comp resistor at very low temperatures is exponential in the square root of 1/T. Such things are used as thermometers. For plotting the calibration curve, it's really nice to have a straight line plot, plotted as a function of 1/√T, with ticks labeled in units of T. Case 4: If you want to get serious, consider tilted ticks and iso-contours as in any ternary plot: http://en.wikipedia.org/wiki/Ternary_plot Case 5: Tilted ticks and iso-contours due to rotation in the XY plane, e.g. magnetic north versus geographical north. Case 6: Tilted ticks and iso-contours due to rotation in the XT plane in spacetime, using /hyperbolic/ trigonometry. https://www.av8n.com/physics/axes.htm#sec-spacetime Case 7: If you want to get really serious, consider the task of labeling all *four* sets of iso-contours in a chart such as this psychrometric chart: https://www.av8n.com/physics/axes.htm#fig-PsychrometricChart-SeaLevel-SI Case 8: Similarly, the *four* sets of iso-contours in a thermodynamic "indicator diagram" such as https://www.av8n.com/physics/thermo/path-cycle.html#fig-path-pv =========================== I could go on, but I reckon you get the idea. There are a lot of serious real-world applications for tick-marks and iso-contours that are not simply linear in X or logarithmic in X.

**Follow-Ups**:**Re: manual ticks of an axis***From:*Jean Brefort

**References**:**manual ticks of an axis***From:*Frédéric Parrenin

**Re: manual ticks of an axis***From:*Jean Brefort

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