MATLAB: Error using str2sym (line 83) Unable to convert string to symbolic expression: L 1 (C 103): BADCH: Invalid character(s).

str2sym

Hi everyone, I am unsuccessful in converting string to symbolic expression on this code:

https://www.dropbox.com/s/xuauj97inby8o5m/IntegratedModelAnalytical.m?dl=0

What can I do?

Best Answer

You are using the Unicode ‘En Dash’ (decimal 8211, hex 2013) instead of a normal hyphen (decimal 45, hex 002D) for your minus and negation signs.

You also have a ‘hanging’ negative:

Eq1 = ('n + 2*d -((e*6.24*n)/(n^2 +6.24*n + 6.24*5.68e-5))- 2*((e*6.24*5.68e-5)/(n^2 + 6.24*n + 6.24*5.68e-5))–((h*1.7e-3*n)/(n^2 + 1.7e-3*n + 1.7e-3*6.55e-8))– 2*((h*1.7e-3*6.55e-8-)/(n^2 + 1.7e-3*n + 1.7e-3*6.55e-8))- 5.3e-8/n=0');
(SCROLL RIGHT) →                                                                                                                                                                     ↑ ← HERE

The correct version is:

Eq1 = 'n + 2*d - ((e*6.24*n)/(n^2 + 6.24*n + 6.24*5.68e-5)) - 2*((e*6.24*5.68e-5)/(n^2 + 6.24*n + 6.24*5.68e-5))-((h*1.7e-3*n)/(n^2 + 1.7e-3*n + 1.7e-3*6.55e-8)) - 2*((h*1.7e-3*6.55e-8)/(n^2 + 1.7e-3*n + 1.7e-3*6.55e-8)) - 5.3e-8/n=0';

There are other problems. I will let you solve them.

Related Solutions

MATLAB: Error using sym/cat>checkDimensions (line 70) CAT arguments dimensions not consistent.

I did not troubleshoot all the errors that might be in your code, only the ones in the ‘eqs’ vector. Spaces are important, and please do not use continuation ellipses when you intend a new line. Rather than manually remove the spaces, I just put every line in parentheses. Note that the continuation line in the ‘diff(v(t),t) ==’ line, there is a missing operator. I used a + creating ‘+ n(t)’, so if I guessed wrong, replace it appropriately.

Try this version of ‘eqs’:

eqs = [(diff(c(t),t) == 1 / 1.5e-6 * (1.666667e-5 * 6.51332e-2 - 1.666667e-5 * c(t)) - ((c(t) * 8.314 * 323.15 - 149 * b(t)) / (1 / 4.14e-6) + (149 / ((1 + (1.39e-9 * d(t)) / (2.89e-9 * e(t))) * 8.4e-4))) );
(diff(g(t),t) == 1/1.5e-6 * (-1.666667e-5 * g(t)) -( 9.598e-4 * ( 1 + (1.39e-9 * d(t)) /( 3.53e-9 * h(t))) * (g(t) * 8.314 * 323.15 / 5.15e3 - i(t))) );
(diff(e(t),t) == ((c(t) * 8.314 * 323.15 - 149 * b(t)) / (1 / 4.14e-6) + ( 149 / ((1 + (1.39e-9 * d(t)) / ( 2.89e-9 * e(t))) * 8.4e-4)) - (0.162 * exp(5153/323.15) * (((d(t) * k(t)) / 1.07e-7) - 1) * (10 / ((d(t) * k(t)) / 1.07e-7)))) );
(diff(h(t),t) == (9.598e-4 * ( 1 + (1.39e-9 * d(t)) / (3.53e-9 * h(t))) * (g(t) * 8.314 * 323.15 / 5.15e3 - i(t))) - (-8.825e-3 * 12.54 * 100.0869 * m(t) * n(t) * (1-(0.84*n(t)) / (1 + 0.84 * n(t)))) );
(diff(u(t),t) == (-8.825e-3 * 12.54 * 100.0869 * m(t) * n(t) * (1 - (0.84 * n(t)) /(1 + 0.84 * n(t)))) - (0.162 * exp(-5153/323.15) * (((d(t) * k(t)) / 1.07e-7) - 1 * (10 /((d(t) * k(t)) / 1.07e-7)))) );
(diff(m(t),t) == -m(t) * (-8.825e-3 * 12.54 * 100.0869 * m(t) * n(t) * ( 1 - (0.84 * n(t)) / (1 + 0.84 * n(t)))) * 100.0869 / 2703 );
(diff(v(t),t) == (-8.825e-3 * 12.54 * 100.0869  * m(t) * n(t) * (1 - (0.84 * n(t)) / (1 + 0.84 * n(t)))) * 258.30 / 2540 ...
+ n(t) +  2 * d(t) - ((e(t) * 6.24 * n(t)) / (n(t)^2 + 6.24 * n(t) + 6.24 * 5.68e-5)) -  2 * ((e(t) * 6.24 * 5.68e-5) / (n(t)^2 + 6.24 * n(t) + 6.24 * 5.68e-5)) - ((h(t) * 1.7e-3 *n(t)) / (n(t)^2 + 1.7e-3 * n(t) + 1.7e-3 * 6.55e-8)) - 2 * ((h(t) * 1.7e-3 * 6.55e-8) / (n(t)^2 + 1.7e-3 * n(t) + 1.7e-3 * 6.55e-8)) - 5.3e-8 / n(t) == 0) ;
(1.7e-3 == n(t) * r(t) / i(t) );
(6.55e-8 == n(t) * s(t) / r(t) );
(6.24 == n(t) * q(t) / b(t) );
(5.68e-5 == n(t) * k(t) / q(t) );
(5.3e-8 == n(t) * tt(t) );
(e(t) == b(t) + q(t) + k(t) );
(h(t) == i(t) + r(t) + s(t) );
(u(t) == i(t) + r(t) + s(t))];

If you want ‘eqs’ to be a row vector instead of a column vector, replace the semicolons at the end of each line with commas.

MATLAB: This DAE appears to be of index greater than 1.

You try to solve

dy(1)/dt = 1/A*(B*C-B*y(3))–((y(3)*D*E-F*y(2))/(1/G)+(F/((1+ (H*y(4))/(I*y(5)))*J))
dy(2)/dt = 1/A*(-B*y(7))–(K*(1+(H*y(4))/(MM*y(8)))(y(7)*D*E/L–y(9)))
...

not

dy(3)/dt = 1/A*(B*C-B*y(3))–((y(3)*D*E-F*y(2))/(1/G)+(F/((1+ (H*y(4))/(I*y(5)))*J))
dy(7)/dt = 1/A*(-B*y(7))–(K*(1+(H*y(4))/(MM*y(8)))(y(7)*D*E/L–y(9)))
...

Best Answer

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MATLAB: Error using sym/cat>checkDimensions (line 70) CAT arguments dimensions not consistent.

MATLAB: This DAE appears to be of index greater than 1.

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