Program Sudden Errors Appearing

This program I wrote was working just fine, but then upgraded to Matlab 2017 and these errors appear (see pic attachment). My program is attached as well. How do I fix this error?

Answer 1

[Walter Roberson]

You installed Maple after you installed MATLAB, and you gave permission for Maple to install the Maple Symbolic Toolbox for MATLAB, which defines sym() and solve() and some other routines but uses symbolic equations differently than MATLAB's Symbolic Toolbox does. Your code defines eqn1 and eqn2 using the form

eqn1 = one_expression == another_expression

which is valid in MATLAB's Symbolic Toolbox meaning "construct a symbolic expression with two parts joined by the "==" operator that can be reasoned about later." When you have Maple's symbolic toolbox, this is instead interpreted as "test now whether the two expressions are exactly the same and assign logical false to eqn1 now if they are different and logical true to eqn1 now if they are the same".

The solution is to either remove the Maple symbolic toolbox for MATLAB, or else to use pathtool to push it down to lower priority than MATLAB's Symbolic Toolbox.

[Kelly McGuire]

Is there a way to remove Maple symbolic toolbox without having to uninstall Matlab?

[Walter Roberson]

Yes. If you use

which -all sym

you should be able to find the directory that the Maple version is stored in. You can then remove those directories. Or use pathtool to remove them from your MATLAB path. (Note: if you just remove them from your MATLAB path then if you later do a restoredefaultpath then they are likely to re-appear.)

If I recall correctly, the Maple symbolic toolbox also comes with its own uninstaller, but at the moment I do not recall which directory that is stored in. (I do have Maple but it has been a few years since I installed the Maple symbolic toolbox for MATLAB.)

[Kelly McGuire]

Ok, thanks for the response.

[Kelly McGuire]

I uninstalled Maple to get rid of the Maple symbolic toolbox, and now I get a new error. See pic attachment.

[Walter Roberson]

I ran your code with some random values for the boxes, and did not observe any crash.

The object being complained about, handles.rate, does exist and is a uicontrol of style 'text'.