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Customizing axes part 5 – origin crossover and labels

Posted By Yair Altman On July 27, 2016 | __6 Comments__

When HG2 graphics was finally released in R2014b, I posted a series of articles about various undocumented ways by which we can customize Matlab’s new graphic axes: rulers (axles) ^{[3]}, baseline, box-frame, grid ^{[4]}, back-drop ^{[5]}, and other aspects ^{[6]}. Today I extend this series by showing how we can customize the axes rulers’ crossover location.

Until R2015b, we could only specify the axes’ **YAxisLocation** as `'left'`

(default) or `'right'`

, and **XAxisLocation** as `'bottom'`

(default) or `'top'`

. For example:

x = -2*pi : .01 : 2*pi; plot(x, sin(x)); hAxis = gca; hAxis.YAxisLocation = 'left'; % 'left' (default) or 'right' hAxis.XAxisLocation = 'bottom'; % 'bottom' (default) or 'top'

The crossover location is *non-fixed* in the sense that if we zoom or pan the plot, the axes crossover will remain at the bottom-left corner, which changes its coordinates depending on the X and Y axes limits.

Since R2016a ^{[7]}, we can also specify `'origin'`

for either of these properties, such that the X and/or Y axes pass through the chart origin (0,0) location. For example, move the **YAxisLocation** to the origin:

hAxis.YAxisLocation = 'origin';

And similarly also for **XAxisLocation**:

hAxis.XAxisLocation = 'origin';

The axes crossover location is now fixed at the origin (0,0), so as we move or pan the plot, the crossover location changes its position in the chart area, without changing its coordinates. This functionality has existed in other graphic packages (outside Matlab) for a long time and until now required quite a bit of coding to emulate in Matlab, so I’m glad that we now have it in Matlab by simply updating a single property value. MathWorks did a very nice job here of dynamically updating the axles, ticks and labels as we pan (drag) the plot towards the edges – try it out!

So far for the documented stuff. The undocumented aspect is that we are not limited to using the (0,0) origin point as the fixed axes crossover location. We can use any x,y crossover location, using the **FirstCrossoverValue** property of the axes’ hidden **XRuler** and **YRuler** properties. In fact, **we could do this since R2014b**, when the new HG2 graphics engine was released, not just starting in R2016a!

% Set a fixed crossover location of (pi/2,-0.4) hAxis.YRuler.FirstCrossoverValue = pi/2; hAxis.XRuler.FirstCrossoverValue = -0.4;

For some reason (bug?), setting **XAxisLocation**/**YAxisLocation** to ‘origin’ has no visible effect in 3D plots, nor is there any corresponding **ZAxisLocation** property. Luckily, we can set the axes crossover location(s) in 3D plots using **FirstCrossoverValue** just as easily as for 2D plots. The rulers also have a **SecondCrossoverValue** property (default = -inf) that controls the Z-axis crossover, as Yaroslav pointed out ^{[8]} in a comment below. For example:

N = 49; x = linspace(-10,10,N); M = peaks(N); mesh(x,x,M);

hAxis.XRuler.FirstCrossoverValue = 0; % X crossover with Y axis hAxis.YRuler.FirstCrossoverValue = 0; % Y crossover with X axis hAxis.ZRuler.FirstCrossoverValue = 0; % Z crossover with X axis hAxis.ZRuler.SecondCrossoverValue = 0; % Z crossover with Y axis

hAxis.XRuler.SecondCrossoverValue = 0; % X crossover with Z axis hAxis.YRuler.SecondCrossoverValue = 0; % Y crossover with Z axis

Users will encounter the following unexpected behavior (bug?) when using either the documented ***AxisLocation** or the undocumented **FirstCrossoverValue** properties: when setting an x-label (using the * xlabel* function, or the internal axes properties), the label moves from the center of the axes (as happens when

In such cases, we would expect the labels locations to be reversed, with the main label on the left and the secondary label in its customary location on the right. The exact same situation occurs with the Y labels, where the main label unexpectedly appears at the top and the secondary at the bottom. Hopefully MathWorks will fix this in the next release (it is probably too late to make it into R2016b, but hopefully R2017a). Until then, we can simply switch the strings of the main and secondary label to make them appear at the expected locations:

% Switch the Y-axes labels: ylabel(hAxis, '\times10^{3}'); % display secondary ylabel (x10^3) at top set(hAxis.YRuler.SecondaryLabel, 'Visible','on', 'String','main y-label'); % main label at bottom % Switch the X-axes labels: xlabel(hAxis, '2^{nd} label'); % display secondary xlabel at right set(hAxis.XRuler.SecondaryLabel, 'Visible','on', 'String','xlabel'); % main label at left

As can be seen from the screenshot, there’s an additional nuisance: the main label appears a bit larger than the axes font size (the secondary label uses the correct font size). This is because by default Matlab uses a 110% font-size for the main axes label, ostensibly to make them stand out. We can modify this default factor using the rulers’ hidden **LabelFontSizeMultiplier** property (default=1.1). For example:

hAxis.YRuler.LabelFontSizeMultiplier = 1; % use 100% font-size (same as tick labels) hAxis.XRuler.LabelFontSizeMultiplier = 0.8; % use 80% (smaller than standard) font-size

Note: I described the ruler objects ^{[3]} in my first article of the axes series. Feel free to read it for more ideas on customizing the axes rulers.

Categories: Handle graphics, Low risk of breaking in future versions, Stock Matlab function, Undocumented feature

6 Comments (Open | Close)

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URL to article: **https://undocumentedmatlab.com/blog/customizing-axes-part-5-origin-crossover-and-labels**

URLs in this post:

[1] Image: **http://undocumentedmatlab.com/feed/**

[2] **email feed**: **http://undocumentedmatlab.com/subscribe_email.html**

[3] rulers (axles): **https://undocumentedmatlab.com/blog/customizing-axes-rulers**

[4] baseline, box-frame, grid: **https://undocumentedmatlab.com/blog/customizing-axes-part-2**

[5] back-drop: **https://undocumentedmatlab.com/blog/customizing-axes-part-3-backdrop**

[6] other aspects: **https://undocumentedmatlab.com/blog/customizing-axes-part-4-additional-properties**

[7] Since R2016a: **http://www.mathworks.com/help/matlab/ref/axes-properties.html#property_xaxislocation**

[8] pointed out: **https://undocumentedmatlab.com/blog/customizing-axes-part-5-origin-crossover-and-labels#comment-384290**

[9] Undocumented scatter plot jitter : **https://undocumentedmatlab.com/blog/undocumented-scatter-plot-jitter**

[10] HG2 update : **https://undocumentedmatlab.com/blog/hg2-update**

[11] Draggable plot data-tips : **https://undocumentedmatlab.com/blog/draggable-plot-data-tips**

[12] Plot line transparency and color gradient : **https://undocumentedmatlab.com/blog/plot-line-transparency-and-color-gradient**

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6 Comments To "Customizing axes part 5 – origin crossover and labels"

#1 CommentByYaroslavOn July 28, 2016 @ 12:36 amHi Yair,

Great post yet again. It is worth mentioning that your methods can be extended to 3 dimensional plots, which are currently unsupported. For example,

#2 CommentByYair AltmanOn July 28, 2016 @ 10:44 am@Yaroslav – thanks! I updated the text accordingly.

#3 CommentByGuillaume De LescluzeOn November 6, 2016 @ 10:08 amHi Yarasov/Yair,

Context: I am using R2015a to display a ternary three-dimensional plot, so I have a base equilateral triangle and a vertical axis on top of this.

My question: When copying the above code in Matlab, I get an error when using the “ZRuler” command.

Do you have an idea why it might not be working in my case?

Many thanks!

#4 CommentByFrank BrownOn August 17, 2016 @ 5:34 pmYair,

Great site!

I have been moving axes to cross at the origin as part of plotting for years and I’m glad to see MATLAB adopt this capability. One question though.

How could I make this the default behavior?

Does not work in 2015b, though the property exists and can be modified. Also similar syntax works for other axes properties (‘DefaultAxesLineWidth’).

Thanks for the help,

Frank

#5 CommentByYair AltmanOn August 17, 2016 @ 9:25 pm@Frank –

(you forgot the “Axes” part in ‘default

AxesYAxisLocation’)#6 CommentBySarahOn August 9, 2018 @ 7:54 pmThank you!