Saad - you could try opening the figure and then grab the handles for the graphics object (or objects) that were drawn on the axes (of that figure). For example, suppose we do
x = -2*pi:0.01:2*pi;
y = sin(x);
h = plot(x,y);
saveas(h,'mySinePlot.fig');
So we have drawn the familiar sine curve and then saved the figure to a file. Now, we open the figure as
close all;
open mySinePlot.fig;
If we assume that there is just one child object (for the figure) and that it is the axes, then we could do
hFigAxes = get(gcf,'Children');
We now grab the children for the axes. Given our very simple example, there will be just one child from which we can get the x and y data that we used when calling plot
hSinePlot = get(hFigAxes,'Children');
xData = get(hSinePlot,'XData');
yData = get(hSinePlot,'YData');
If you do the same for the other figure, then you will be able to obtain both sets of x- and y-data of which you can then plot onto the same figure.
Your plots may not be as simple as the above, but start with this code and see what happens. If your axes has more than one child, then loop through all of the children until you find the one that you are looking for (if a plot, then its type is Line).
