How do I set YAxis of Axes from a numeric ruler to a datetime ruler?

I would like to dynamically set the Yaxis to a datetime ruler.

Example Code:

figure;
aa=axes;
set(aa,'YAxis', matlab.graphics.axis.decorator.DatetimeRuler);

I get the following error:

Error

Error using matlab.graphics.axis.Axes/set

You cannot set the read-only property 'YAxis' of Axes.

I was able to set the xaxis to a datetime ruler but, the yaxis is set as read-only for some reason.

[nanren888]

Z does not complain but gives a strange result :)

[dpb]

I'm guessing this is a non-supported feature that TMW expects that if you want a datetimeruler axis that you'll create the axis with such. Doc for the axes object implies such.

Seems like there could be a time and place to be able to do this programmatically, I'd agree...submit enhancement request.

[nanren888]

Will datetick() do?

I know, just another numeric ruler, but it does some things.

Answer 1

[Cris LaPierre]

This can be handled automatically if your Y variable is a datetime.

td = datetime(datestr(now + [0:10]'),'Format','MMM-dd');
x = 0:10;
plot(x,td)

[Victor Esparza]

Yes - ideally the way you listed would be best but, for my application, the ruler needs to be updated dynamically from a numeric type to a datetime type. Thank you for your input. Any work around would also we welcomed.

[dpb]

Why is it totally impossible to create the axes with the desired axes type? Somewhat inconvenient perhaps, but I don't see where it would be impossible by reworking how the axes object is created.

[Cris LaPierre]

In 18b, the following command will change the ruler to DateTime

set(aa,'YRuler',matlab.graphics.axis.decorator.DatetimeRuler)

However, as soon as I plot numeric data, the ruler automatically changes back to Numeric. I haven't tested it exhaustively yet, but you may need to plot datetime data to keep your ruler datetime even if you find a workaround.

The other suggestion I might have, then, is to start by plotting a datetime like I showed up above. Capture the plot in a handle. Then, when you want to dynamically update your plot, just update the XData and YData of the line instead of replotting.

td = datetime(datestr(now + [0:10]'),'Format','MMM-dd');
x = 0:10;
h = plot(x,td);
...
h.XData = randi(100,1,10);
h.YData = randi(20,1,10);

At least from quick testing for me, this does not change the YAxis ruler.

[Adam Danz]

Another undocumented method of ruler conversion to numeric, datetime, duration or categorical:

% ax is the axis handle
ax = axes(); 
% samp is a sample of data used to format the axis ruler
% and must be numeric, datetime, duration, categorical 
% array or an objects which can be converted to double. 
samp = datetime(datestr(now + [0:10]'),'Format','MMM-dd');

% To change x axis
matlab.graphics.internal.configureAxes(ax, samp, 1)

% To change y axis
matlab.graphics.internal.configureAxes(ax, 1, samp)

% To change both x and y axes
matlab.graphics.internal.configureAxes(ax, samp, samp)

And it works for other data types such as categorical

samp = categorical({'A', 'B', 'C'});
matlab.graphics.internal.configureAxes(ax, samp, 1)     % x axis
matlab.graphics.internal.configureAxes(ax, 1, samp)     % y axis
matlab.graphics.internal.configureAxes(ax, samp, samp)  % x & y axis

And with mixed ruler types between x and y axes

samp_x = categorical({'A', 'B', 'C'});
samp_y = datetime(datestr(now + [0:10]'),'Format','MMM-dd');
matlab.graphics.internal.configureAxes(ax, samp_x, samp_y)

[Eric Delgado]

Unfortunately it is not possible to change the ruler of an axes. It is a read only property. The simplest and natural solution is just put a new data under the old data.

fig = figure;
ax = axes(fig);

data1 = line(ax, 1:10, linspace(datetime([2020 12 01]), datetime([2020 12 10]), 10))
ax.YAxis
% You have a datetime ruler axes.

cla
data1 = line(ax, 1:10, 1:10)
ax.YAxis
% And now you have a numerical ruler axes.

[Adam Danz]

> Unfortunately it is not possible to change the ruler of an axes

Yes it is, in at least some contexts. Cris and I both share methods directly above.

To clarify your solution, cla() is the only reason it works. When you clear the axis, it's a blank slate and the axes will respond to the data classes again. If you remove cla from your answer, it no longer works. But it's a good point. Clearing the axis is a solution. But it doesn't really convert the axes. It just resets them.