Solving an implicit equation with fsolve and validating with fplot
20 Ansichten (letzte 30 Tage)
Ältere Kommentare anzeigen
Ryan McBurney
am 29 Jan. 2021
Beantwortet: Ryan McBurney
am 1 Feb. 2021
Below is my code to try and solve this function:
D/(log10(RX*cfe)-C))^2 = cfe
I'm not sure if I'm using fsolve correctly. I get a value for cfe as 0.0016 but when I try to some validation by plotting two sides of the equation the curves cross at .0017377. That's about a 7% difference in values so I am questioning if I'm using fsove correctly.
I'm actually unsure of how to implement the initial guess which I call cfi.
I thought maybe adjusting the options would make the code run longer and would get a closer answer to the plotting method, but I'm not even sure if I'm doing that right.
Any direction would be helpful.
% AL, BE, E, and TWTD are all constants, which makes D and C also constants.
D = 0.242*(asin(AL)+asin(BE))/sqrt(E);
C = 1.26*log10(TWTD);
RX = 3.5e6 % Constant
options = optimoptions('fsolve','FunctionTolerance',1.0000e-1);
cfi = .455/(log10(RX))^2.58; % Initial guess
f = @(cfe,cfi) (D/(log10(RX*cfi)-C))^2 - cfe;
fsol = fsolve(@(cfe) f(cfe,cfi),0,options);
%------------------------------------------------------
syms cfe
eqnLeft = 0.242*(asin(AL)+asin(BE))/(log10(RX*cfe)-C);
eqnRight = sqrt(cfe)*sqrt(E);
fplot([eqnLeft eqnRight])
title([texlabel(eqnLeft) ' = ' texlabel(eqnRight)])
0 Kommentare
Akzeptierte Antwort
Weitere Antworten (1)
Alan Weiss
am 31 Jan. 2021
Bearbeitet: Alan Weiss
am 31 Jan. 2021
You have set an enormous value of the FunctionTolerance option. Don't set any options and I expect that you will get a better answer.
If this advice does not help, then please give numeric values for your constants so that we might have a chance at running your code and seeing what is happening.
Alan Weiss
MATLAB mathematical toolbox documentation
1 Kommentar
Siehe auch
Kategorien
Mehr zu Calculus finden Sie in Help Center und File Exchange
Produkte
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!