Get a point from a graph

Hie guys, I have done a GUI to plot a graph. Now i would like to get the calue from the graph. Lets say i plot(x,y). I would like to get the value out, for example when x=4, what is the value of y. I know there is a datacursormode, but it only show me the value in the graph. In this case, i would like to get the value in the command window.

Thanks Ean

Answer 1

[Paulo Silva]

You can retrieve the plotted data, for example:

XData=get(get(gca,'children'),'XData');
YData=get(get(gca,'children'),'YData');

Now if you want to know the y value when x=4 just do

YData(XData==4)

[Matt Fig]

Note that the final line may fail. If you get an empty value for that line, use the INTERP1 function instead.

y_4 = interp1(XData,YData,4);

[Ean Soo]

Hie, the children there is it refers to the axes name?

[Matt Fig]

For example:

x = -4:.1:4;

y = x.^2;

plot(x,y)

XData=get(get(gca,'children'),'XData');

YData=get(get(gca,'children'),'YData');

% Get y value for x=3.33 - NOT a data point.

y_3p33 = interp1(XData,YData,3.33,'spline')

[Paulo Silva]

Children in that case refers to the Line made by the plot.

[Ean Soo]

Thank You, your code help me a lot.

[Nasiru Umar Bagudu]

What if i want to get the value of x when y is zero for example?

Answer 2

[Walter Roberson]

You can use a custom datacursormode callback that includes display() in its code.

[Ean Soo]

Erm, is not suitable for me in this case because i would want to recall a very precise value like 12.22. I still working on how to recall that thing. Is just didnt work..