MATLAB: update surface plot and change location of line objects in while loop

Question

So I am encountering a couple errors and am not sure where they're coming from. I won't post the whole code, but I will do my best to explain (fear I will be accused of plagiarism).

The assignment is to create a window with two plots: a surface plot and a contour plot. The surface plot represents elevation of a portion of the map represented by the contour plot. The portion is indicated by a blue box on the contour plot. I've successfully plotted the surface and contour plots and have identified the first area with a blue box. However, now I need to implement a menu system wherein the user enters 1, 2, 3, or 4 to move the box north, south, east or west.

Here is how I instantiated the plots:

fig = figure(1);
[xGrid, yGrid] = meshgrid(xMeters(xStart:xEnd), yMeters(yStart:yEnd));

%surface plot
elevationBox = ELEV(xStart:xEnd, yStart:yEnd);
surface = subplot(2, 1, 1);
surf(xGrid, yGrid, elevationBox);
axis([0 max(xGrid(:)) 0 max(yGrid(:)) min(elevationBox(:)) max(elevationBox(:))]);
axis tight;

%contour plot
elevation = ELEV;
[xMap, yMap] = meshgrid(xMeters(1:335), yMeters(1:230));
map = subplot(2, 1, 2); contour(xMap, yMap, elevation);
axis([0 max(xMeters(:)) 0 max(yMeters(:))]);
axis fill;
set(fig, 'Position', [500 100 600 700]);

right = line(xRight, xLeft);
left = line(xLeft, yLeft);
top = line(xTop, yTop);
bottom = line(xBottom, yBottom);

So all that works fine. Obviously I didn't include the parts where I defined the data and everything. After this comes a switch statement that changes the values of xLeft, yLeft, etc as well as xStart, xEnd etc.

Here is my attempt to update the plots:

[xGrid, yGrid] = meshgrid(xMeters(xStart:xEnd), yMeters(yStart:yEnd));
elevationBox = ELEV(xStart:xEnd, yStart:yEnd);
subplot(2, 1, 1)
    set(surface, 'XData', xGrid, 'YData', yGrid, 'ZData', elevationBox);

drawnow;

I can choose an option and there is no error, but the plot doesn't update and when I quit the program I get this error:

Error using matlab.graphics.axis.Axes/set

There is no XData property on the Axes class.

Error in A9 (line 129)

set(surface, 'XData', xGrid);

The setting is inside the while loop but outside the switch statement. I also had a few lines using set on the line objects but those weren't working either so I thought I'd focus here first. I'm figuring whatever I'm doing wrong applies to both object types but if not let me know.

Thanks!

kmac kmac · Accepted Answer · 2015-11-18T20:20:47

Rather than grab a handle to the axis (which you call surface), you want the data object. So grab a handle at surf_h = surf(...);.

A little example:

% Generate a random surface grid
n = 10;
[x, y] = meshgrid(1:n, 1:n);
z = rand(n);

% Plot
fig_h = figure(1);
axis_h = subplot(2, 1, 1);
surf_h = surf(x,y,z);

% Modify XData
set(surf_h, 'XData', -x);
drawnow;

MATLAB: update surface plot and change location of line objects in while loop

1 Answers