Two things are happening here: There is a nested function, and a function handle. The function handle (the @ symbol creates it) snapshots the workspace of the main function upon creation. This is how the variable stay “alive”. The scoping into the nested function is as discussed in my video.

Thanks for a great question!
Doug

In your demo the main function has ended. I thought when the function ends all its variables die.

The nested function is called through a callback, why does the callback revive the main function?

Thanks again,

Yonathan

hdd and hdp were in scope in the highlightPair function because it is a nested function and has access to the variables of the outer function. See this video for more details:

http://blogs.mathworks.com/pick/2008/02/01/matlab-basics-nested-functions/

Thanks,
Doug

Nice video, One question though:

How does the “highlightPair” function knows the variables hdd & hdp?

Thanks,

Yonathan

This will get you the current point that you click on. An example like this was done here:

http://blogs.mathworks.com/pick/2007/12/26/advanced-matlab-buttondownfcn/

Is there a similar way to do this with a ‘line’ instead of a ‘point’. If I were to make a line with a ButtdownFnc is there a way I could get the (x,y) coordinates of the clicking? I see that I could potentially plot each of the points individually as you did above, but it seems like there might be a more elegant way to do this.

Thanks

Thanks for adding to this with your technique.

Doug

You can even store more information in the userdata field using a struct. It just needs some discipline and little more lines of code for adding or updating data:

str = get(gcf, ‘userdata’);
str.myfield = something;
set(gcf, ‘userdata’, str);

Markus

Sorry no, that was just video editing. In an effort to keep the video shorter this time, I was cutting out parts where I was silently typing. I highlighted them blue in an effort to give an idea that I was ‘faking it’.

Sorry for the confusion!

Doug

Thanks