MATLAB Answers


Program Sudden Errors Appearing

Asked by Kelly McGuire on 29 Sep 2017
Latest activity Commented on by Walter Roberson
on 29 Sep 2017
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?


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1 Answer

Answer by Walter Roberson
on 29 Sep 2017
 Accepted Answer

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.


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

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