Adding specific point info in MATLAB

Question

I'm plotting the magnitude and phase response of a notch filter I designed and I need to mark the cutoff frequencies as well as the notch frequency point. I'd like to show the same information that shows up if you click on a plot. Is there a way to force MATLAB to show boxes like the one that shows up if you click on a point?

I have attached an image showing what I mean. I'd like to get a box like that at specific frequency points that I choose.

Answer 1

Here an example I built for an exponential function:

clear all

figure
f = plot(exp(1:10));

datacursormode on

% get the handle of the data cursor 
hdc = get(gcf,'WindowButtonDownFcn');
dcm = hdc{3}{2};


props.Position = [min(exp(1:10)) log(min(f)) 1];

dcm.createDatatip(f,props);

But you have to generalize the definition of the coordiates for the cursor to your case.

Answer 2

This can actually be done a little more reliably and robustly using some undocumented features of the data cursor ( info ). First we will get the figure's underlying datacursormode and then use that to add and move datatips (like the one in your figure).

fig = figure();

% Plot some fake data for now
xdata = linspace(0, 2*pi, 100);
ydata = sin(xdata);

hLine = plot(xdata, ydata);

% Get the datacursormode of the current figure and enable it
cursorMode = datacursormode(gcf);
set(cursorMode, 'enable','on')

Now that we have the datacursormode object, we can use it to add some new datatips.

datatip = cursorMode.createDatatip(handle(hLine));
% X,Y position at which to place the datatip
set(datatip, 'Position', [xdata(50), ydata(50)]);

We can move this datatip again if we want.

set(datatip, 'Position', [xdata(1), ydata(1)]);

The really nice thing, is that using the cursorMode object we can also create more datatips

datatip2 = cursorMode.createDatatip(handle(hLine));
set(datatip2, 'Position', [xdata(75), ydata(75)])

By combining this information with your own plots and data, you should be able to automatically place the datatips that you need reliably.