How do I toggle images in the GUI

I am a current student and am relatively new to MATLAB. I am currently using an accelerometer as controller.

What I am trying to do is to replace an image when the accelerometer reads a value greater then a set threshold and return to the original image when it is not. This is what I currently have in a while loop

if handles.thresholdValue <= handles.gxFiltdata;

              axes(handles.axes9);
              imshow('RED.JPEG');
          else
              axes(handles.axes9);
              imshow('BLACK.JPEG');
          end

As of right now the image starts off black and turns red and stays red regardless of whether or not the accelerometer reads above or below the threshold set

Answer 1

[Image Analyst]

Put this before your if statement

fprintf('thresh=%f, gxFilt=%f\n', handles.thresholdValue, handles.gxFiltdata)

What does it show in the command window? Next, go here and watch it: http://blogs.mathworks.com/videos/category/gui-or-guide/

[Jeffrey]

I preset my handles.thresholdValue to .7. When I look into the command window it states

thresh=-0.594340, gxFilt=-1.707547
thresh=1.084906, gxFilt=-0.905660
thresh=-0.905660, gxFilt=0.518868
thresh=-1.150943, gxFilt=0.943396
thresh=0.896226, gxFilt=0.896226
thresh=0.886792, gxFilt=>>

Is the "thresh" value suppose to fluxuate with the accelerometer reading "gxFilt" value?

[Image Analyst]

It is changing somehow, somewhere. But I don't know when/where. I suggest you search for all "handles.thresholdValue" in your code and see where an equal sign follows that, meaning that you are setting it to some new value.

[Jeffrey]

Even when I change the if statement to

'if handles.gxdata <= .5;'

The image stays put at red. Is here something wrong with what is inside the loop itself?

[Image Analyst]

Is this an image and you're wanting to change the image to pure red if the image value is less than the threshold and to black if it's above the threshold? If so, you can just do (untested):

binaryImage = (handles.gxFiltdata >= handles.thresholdValue)
imshow(binaryImage);
myColormap = [1,0,0;0,0,0];
colormap(myColormap);
colorbar;