Set and enforce axis properties immediately

I have visualization code along the following lines:

subplot(1, 2, 1);
scatter3(N(:,1), N(:,2), N(:,3), '.');
drawnow;
hold on;  
for r = 1 : NUM
  % ... heavy calculations here
  trisurf(Tri(FBtri), XYZ(:,1), XYZ(:,2), XYZ(:,3));
  drawnow;
  hold on;
end
set(gca, 'XDir', 'reverse');
% End subplot 1

subplot(1, 2, 2);
% Similar code
set(gca, 'XDir', 'reverse');
% End subplot 2

% So on, and so forth...

I need to reverse the X axis, and have found that it only works if I add the property setter after the entire code block for each subplot. This results in the entire subplot being rendered, and then visibly being reversed.

Is there a way that this property can be set and enforced before any contained future objects are computed/rendered, so that everything is shown reversed along the specified axis in the first place?

I would also welcome suggestions towards improving my usage of hold and drawnow, and on how to set and enforce axis reversal (or any axis property in general) for all subplots in the beginning itself with a single call to set, if that's possible.

Answer 1

[Geoff Hayes]

You mention subplots, but your above code does not show that. What are you iterating over? Does NUM correspond to each subplot?

Suppose that you have a figure that you wish to add 16 subplots to. Then you could create the figure with the plots, and reverse the x-axis for each plot.

 figure;                 % create the figure
 m = 4;                  % define the number of subplot rows
 n = 4;                  % define the number of subplot columns
 hSubplots = zeros(m,n); % create an array for the handles to each subplot

 % create/initialize the subplots
 for u=1:m
    for v=1:m
        hSubplots(u,v) = subplot(m,n,(u-1)*n+v);
        hold(hSubplots(u,v),'on');

        % only reverse the x-axis for the first two rows
        if u<=2
            set(hSubplots(u,v),'XDir','reverse');
        end
    end
 end

A figure is displayed with sixteen subplots, with the x-axis reversed for all subplots in the first two rows. Now let's plot some data for each subplot

 % create/initialize the subplots
 [x,y] = meshgrid(1:15,1:15);
 tri = delaunay(x,y);
 z = peaks(15);

 for u=1:m
    for v=1:m
        trisurf(tri,x,y,z,'Parent',hSubplots(u,v))
        axis(hSubplots(u,v),'tight');
    end
 end

After running the second block of code, we can see that the 8 subplots whose x-axes was reversed still maintains that "reversal" after the trisurf displayed the triangles on that subplot.

You should be able to use the above code as a guide to do the same for your work so that everything is shown reversed along the specified axis in the first place.

[slaiyer]

An oversight on my part. I have updated the original post with better indicative code. NUM has nothing to do with the subplots themselves, but is used for iterating over objects within each subplot.

My aim is to have objects in each subplot rendered inverted with each call to drawnow inside the loop (that is, as soon as each one is computed), so that they are not visibly reversed as a whole at the end of the subplot.

Do these updates warrant a change in your explanation? I do not wish to come off as lazy, but the simulations leading to visualization are quite time-consuming, and trying an approach intended for some other purpose would hamper ongoing processes. Thanks, in any case.

[Geoff Hayes]

Try my example and see if it meets your needs. Run the first block of code and observe that the axes are reversed. Then run the second block of code and see that afterwards, the directions of the subplots have been enforced.

For your case, just see what happens for the first subplot if you do something like

 h = subplot(1, 2, 1);
 scatter3(N(:,1), N(:,2), N(:,3), '.');
 drawnow;
 hold(h,'on');  
 set(h,'XDir','reverse');

 for r = 1 : NUM
     % ... heavy calculations here
     trisurf(Tri(FBtri), XYZ(:,1), XYZ(:,2), XYZ(:,3));
     drawnow;
 end

Answer 2

[Sean de Wolski]

If you don't need the intermediate updates in the loop, pull the drawnow out of the loop and call it once after setting xdir reverse. This way the graphics are only updated after the loop which will save time and it will only show the final result which includes xdir reversed.

[slaiyer]

That is a deliberate inclusion. I need to have the objects in every subplot rendered as soon as they are computed.

Answer 3

[Robert Cumming]

when you create your subplot set the Xdir then:

 subplot ( 1, 2, 1, 'xdir', 'reverse' );

 % your other code goes here

 subplot(1, 2, 2, 'xdir', 'reverse' );

If this doesn't work it could be due to you use cla - which resets all axes properties, if thats the case then change the default behaviour of the nextplot command (then you dont need hold on).

 subplot ( 1, 2, 1, 'xdir', 'reverse', 'nextplot', 'add' );