How can I calculate and show the average(mean) of the data show in zoom on an Axes GUI?

I want every time you zoom in axes , calculating the average of the data shown in the zoom, and put it in a static text.

Answer 1

[Julie]

Lets assume your data is x and y Whenever the zoom changes (I don't know how you are implementing your zoom but you may need to add a listener or something else)

xl = xlim %note you may need to use a get command here instead, I am not %100 sure how this will interact with the GUI 
%get(handles."your graph",'xlim')
yl=ylim
yt(x<xlim(1) | x>xlim(2) | y<ylim(1) | y>ylim(2))=[];
set(handles."Your Text box",'string',num2str(mean(yt))]