How to reproduce figure through a previously saved figure handle? - matlab

Question

I plotted the distribution of a set of data in a 3d scatter plot.
h = scatter3(D1,D2,D3,'.');
I have saved h but now need to reproduce the graph. What function should I call on h so that I can get the graph without recalculating D1, D2, D3? Because D1, D2, D3 are computationally expensive to re-calculate, I don't want to do it every time when I need a graph.

Answer 1

"Recreating a graph" can be done if you have the following information:
The data used to create the graph
The graph type used
Any optional settings (colors, axes, scaling, orientation, ...)
The "handle" of a graph (or figure) points to the memory where all that information is stored - but it's just a pointer. Unless you save "what is pointed to", it is no use to you. There is a very cool way to achieve this with a single command. After you have created a figure, you can simply type
saveas(gcf, 'myLastGraph.m', 'm');
Instead of gcf ("get current figure" - the handle to the most recently selected figure) you can use whatever the handle is of the graph you want to save (which must still be visible) - for example, h in your code sample. This will create two files in your current directory (if you specify a full path in the second argument, it will create the files in that directory instead):
myLastGraph.fig
myLastGraph.m
Now you can close all your graphs, clear all variables. Next, you can simply run
myLastGraph
from the command line - and your graph will be re-created, using the data that was saved on disk.

Answer 2

If the graph is still open, you can get the Xdata, Ydata and Zdata by using:
XYZCell=get(get(get(h,'currentaxes'),'children'),{'xdata','ydata','zdata'});
Or if you don't want a cell:
XData=get(get(get(gcf,'currentaxes'),'children'),'xdata');
YData=get(get(get(gcf,'currentaxes'),'children'),'ydata');
ZData=get(get(get(gcf,'currentaxes'),'children'),'zdata');
If the graph is closed, h is useless - as far as I'm aware there is no way to reform a graph from a closed figure handle.
Why not use save your variables first?
I1=d1;
I2=d2;
I3=d3;
scatter3(d1,d2,d3,'.');

Answer 3

By "computationally expensive to re-calculate" I'm not sure whether you mean calculating values of D1, D2, D3 or plotting those values. If the calculation is intensive, save the values to the workspace or save them to disk (e.g. print to a file) so you can load them again later for plotting. You can also save the graph as a *.fig file, which you can open and edit later, which might be a good choice if the plotting is the slow part.
There's no way I know of to use the handle (h) to get your data back, once you've closed the window.
With the figure window still open, however, you can use h to pull in the data:
xyzData = get(get(h, 'children'), {'xdata', 'ydata', 'zdata'});
(NB: h = scatter3(D1,D2,D3,'.'); sets h as the handle to the scattergroup. #Hugh Nolan's fine answer requires that h be the handle to the figure.)