"To RESHAPE the number of elements must not change" error during plot
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Dear all,
I have a function (1x1 symfun) S4(t) with a variable of t. It's a very very long expression so I cannot write them here but it is a multi-exponential function.
Then I did:
t = 0:0.0000001:0.00002
y = S4(t)
plot(t,y)
However, I got "To RESHAPE the number of elements must not change". I have no idea where this came from because I have never used the command RESHAPE. Also, the first time around, when S4(t) was a slightly more compact function and rest of the script exactly the same, I did not have this issue.
I think the command "y = S4(t)" is the problem, but I don't see why it's not good. What am I doing wrong?
Thank you
15 comentarios
Jan
el 25 de Jun. de 2017
Ah, the partially contained message might mean, that this is a problem of sym/disp, so only the display in the command window is affected? Then try to supress this output using a semicolon.
Respuesta aceptada
dpb
el 24 de Jun. de 2017
"S4(t)" is symbolic and a (very) long character expression whereas "t" is double vector. plot is trying to turn them both into column vectors but they're not of commensurate lengths so it aborts.
You can try to convert the symbolic expression to numeric first but if it is so long it may not succeed; you may need to reformulate your problem to use numeric solution rather than explicit symbolic. Doing so would probably also reduce your calculation time by orders of magnitude.
2 comentarios
dpb
el 24 de Jun. de 2017
"Do you think vpa would work?"
No, not really, I don't. What have you got to lose to try, however, you've reached/exceeded the limits of practicality and crashed symbolics this way.
I suspect you're going to have to reformulate the solution technique rather than being able to brute-force a direct solution.
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