- Substitute the sym T inside the symbolic engine.
- Evaluate the result using variable-precision arithmetic.
- Convert the result to double.
eval() returns NaN when my matrix gets really big.
2 vues (au cours des 30 derniers jours)
Afficher commentaires plus anciens
Hi
Im making a model of a mass-spring system where I can increase the numbers of masses. I use modal analysis where I transform my eq's into the Q domain and then back again.
My final result is a [n,1] vector where n is the numbers of masses.
When I use:
n = 4 % Number os masses %
T = 1 % Time which is set as "syms T" %
eval(X) % X is my [n,1] vector %
my result is something like:
ans =
0.0158
0.0739
0.1778
0.8150
but when I pick n to be more then 4 i just get "NaN" and I think it is because my vector gets too big for eval()..
When I look at my X vector it looks like this:
(227072026347336273211456024361092029598452603947709420093308928000*sin(T))/3496036292367407553353910200384804229923697463840499539488117510161+..... and it continues likes this for 2 full pages.
What to do?
Thank you!
0 commentaires
Réponse acceptée
Alexander
le 25 Avr 2012
Please try the following:
double(vpa(evalin(symengine, ['subs(' char(X) ', T=' num2str(T) ')'])))
This does the following steps:
2 commentaires
Walter Roberson
le 25 Avr 2012
I think you should probably be able to simplify that to
double(subs(X))
Adilet Nuratay
le 31 Jan 2021
Sorry, I have similar problem.
But I cannot understand the given command. Can anyone clarify it ?
Thank you in advance!
Voir également
Catégories
En savoir plus sur Number Theory dans Help Center et File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!