How to plot several curves in MATLAB using handles

Question

I am plotting data in MATLAB in real time. I want to use a handle. My problem is I do not know how to plot more than one Y-Data Curve.

I found the following code It shows how to plot one set of YData. Has anybody got an idea to transform the code into two or more Y-Datasets, e.g. sind(x) as an additional curve in the plot?

x = 1:1000;
y = cosd(x);

xi = x(1);
yi = y(1);
h = plot(xi, yi, 'YDataSource', 'yi', 'XDataSource', 'xi');

for k = 2:1000...
xi = x(1:k);
yi = y(1:k);
refreshdata(h, 'caller');
drawnow;
end;

Answer 1

The below code works for me, if you really want to use handles

x = 1:1000;
y = cosd(x);
y2 = sind(x);

xi = x(1);
yi = y(1);
yi2 = y2(1);
figure(1); clf;
h = plot(xi, yi, 'YDataSource', 'yi', 'XDataSource', 'xi');
hold on;
h2 = plot(xi, yi2, 'YDataSource', 'yi2', 'XDataSource', 'xi');

for k = 200:1000
    xi = x(1:k);
    yi = y(1:k);
    yi2 = y2(1:k);
    refreshdata(h);
    refreshdata(h2);
    drawnow;
end;

You do need a hold on.

Also, instead of refreshdata you can use set as Andrey suggested:

set(h,'Xdata',xi,'YData',yi);
set(h2,'Xdata',xi,'YData',yi2);

Answer 2

First of all, never use refreshdata. Use the direct set method instead.

        set(h,'Xdata',xi,'YData',yi);

Secondly, you should do two plots

      h1 = plot(xi, yi);
      h2 = plot(xi, yi);

And update each one accordingly.

Answer 3

Are you maybe looking for the hold command?

plot(1 : 10, (1 : 10).^2, 'r')
hold on
plot(1 : 10, (1 : 10).^3)

EDIT:

You can use hold in combination with set to update the plot (see also Andrey's answer):

h1 = plot(1 : 10, (1 : 10).^2, 'r');
hold on;
h2 = plot(1 : 10, (1 : 10).^3);
set(h1, 'XData', 1 : 2 : 20);
set(h2, 'YData', 0.1 * (1 : 20).^3);

The axes will update automatically.

Answer 4

If you don't care too much about displaying the same colour for all curves, simply concatenate the x data into a single vector separated by NaN between the curve components (do a similar thing for the y data). Then the "plot" command can take in these larger x and y vectors and will display everything at once. You may get around the colour issue by doing something similar with the colordata array.