Error with Matlab Solve Function

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Tyler Reohr 2021-9-28

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1462079-error-with-matlab-solve-function

评论： Walter Roberson 2021-9-28

采纳的回答： Walter Roberson

在 MATLAB Online 中打开

I'm trying to solve for the critical points of the Lorenz Equations symbolic (i.e. in terms of

), but keep getting an error that I don't recognize at all when I try to run my code. I ran it on matlab online because I've never had an issue using solve before and it worked fine, but on my own computer (has every Matlab toolbox installed), I couldn't get it to work.

Here's my code:

clear all; close all; clc

syms sigma rho beta x y z; % Symbolic variables to solve system of ODEs

F1 = sigma*y - sigma*x; % First Lorenz ODE

F2 = rho*x - x*z - y; % Second Lorenz ODE

F3 = x*y - beta*z; % Third Lorenz ODE

F0 = [F1;F2;F3]; % Lorenz system of ODEs

critPoints = solve(F0 == 0, [x y z]); % Solves the system for the critical points

% The rest of the code prints it out

critPoints.x

ans =

critPoints.y

ans =

critPoints.z

ans =

It also runs fine here, but for reference here's the exact error message I'm getting when trying to run it on my own computer:

Error using sym/solve (line 89)

Error using maplemex

Error, (in MTM:-solve) Vector(3, [0,0,0], datatype =

integer[1]) is not valid equation or expression

Error in Homework2 (line 14)

critPoints = solve(F0 == 0, [x y z])

I'm using Matlab2021a

Thanks!

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Answer 1

Walter Roberson 2021-9-28

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1462079-error-with-matlab-solve-function#answer_796524

You have Maple installed on your computer and you asked it to install the connection software between MATLAB and Maple. You are not using the Symbolic Toolbox, you are using Maple instead.

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Tyler Reohr 2021-9-28

编辑：Tyler Reohr 2021-9-28

I do have Maple but don't think that I've used it more than one time. Do you know how to unlink the two? I thought it might be useful at somepoint but I don't think I'll ever actually use it.

*Edit*

I tried running the uninstaller, which worked to uninstall the maple toolbox, but now Matlab doesn't seem to recognize it's own symbolic toolbox. I get the following error:

Unrecognized function or variable 'syms'.

Error in Homework2 (line 9)

syms sigma rho beta x y z real;