why do i get Nan as output?
19 visualizzazioni (ultimi 30 giorni)
Mostra commenti meno recenti
im trying to solve four such equations using an input vector containing 4 values.
fn = 1/(rho(1)*Y(1))*(1.113-2.14*Y(1)+2.81*Y(1)^2-1.76*Y(1)^3+0.396*Y(1)^4+0.08694*Y(1)^5-0.0579*Y(1)^6 +0.0077*Y(1)^7);
using ode45.
But the output vector consists of Nan values ; where as its returining numerical values on using the command window.
function file:
function fn = plume5(t,Y)
global rho cp
fn(1) = 1/(rho(1)*cp)*(760.91-1608.08*Y(1)+2449.22*Y(1)^2-2001.61*Y(1)^3+904.51*Y(1)^4-212.087*Y(1)^5+20.095*Y(1)^6);
fn(2) = 1/(rho(2)*cp)*(760.91-1608.08*Y(2)+2449.22*Y(2)^2-2001.61*Y(2)^3+904.51*Y(2)^4-212.087*Y(2)^5+20.095*Y(2)^6);
fn(3) = 1/(rho(3)*cp)*(760.91-1608.08*Y(3)+2449.22*Y(3)^2-2001.61*Y(3)^3+904.51*Y(3)^4-212.087*Y(3)^5+20.095*Y(3)^6);
fn(4) = 1/(rho(4)*cp)*(760.91-1608.08*Y(4)+2449.22*Y(4)^2-2001.61*Y(4)^3+904.51*Y(4)^4-212.087*Y(4)^5+20.095*Y(4)^6);
fn(5) = 1/(rho(5)*Y(5))*(1.113-2.14*Y(5)+2.81*Y(5)^2-1.76*Y(5)^3+0.396*Y(5)^4+0.08694*Y(5)^5-0.0579*Y(5)^6 +0.0077*Y(5)^7);
fn(6) = 1/(rho(6)*Y(6))*(1.113-2.14*Y(6)+2.81*Y(6)^2-1.76*Y(6)^3+0.396*Y(6)^4+0.08694*Y(6)^5-0.0579*Y(6)^6 +0.0077*Y(6)^7);
fn(7) = 1/(rho(7)*Y(7))*(1.113-2.14*Y(7)+2.81*Y(7)^2-1.76*Y(7)^3+0.396*Y(7)^4+0.08694*Y(7)^5-0.0579*Y(7)^6 +0.0077*Y(7)^7);
fn(8) = 1/(rho(8)*Y(8))*(1.113-2.14*Y(8)+2.81*Y(8)^2-1.76*Y(8)^3+0.396*Y(8)^4+0.08694*Y(8)^5-0.0579*Y(8)^6 +0.0077*Y(8)^7);
fn = fn';
main file
clear all
close all
global rho cp
rho = [0.4878;0.7862;1.1449;1.1611;0.4878;0.7862;1.1449;1.1611]
cp = 1.4857
t_span= 0:10
y = [0.0182;0.3105;1.2882;2.7341;0.0182;0.3105;1.2882;2.7341]
[A,P]= ode45('plume5',t_span,y);
2 Commenti
Jan
il 4 Set 2019
Notes: Providing the function to be integrated as CHAR vector is outdated for almost 20 years now. Although it works for reasons of backward compatibility, prefer the "modern" method of function handles.
See Answers: Anonymous for params for using anonymous function to provide parameters. This is much better than using global variables:
rho = [0.4878;0.7862;1.1449;1.1611;0.4878;0.7862;1.1449;1.1611];
cp = 1.4857;
[A,P]= ode45(@(t, Y) plume5(t, Y, roh, cp), t_span, y);
function fn = plume5(t,Y, roh, cp)
...
end
Risposta accettata
Jan
il 4 Set 2019
Modificato: Jan
il 4 Set 2019
Use te debugger to determine the first occurrence of a NaN. Type this in the command window:
dbstop if naninf
Then run the code again. When Matlab stops, check the value of the trajectory. Most likely there is a pole and NaN or Inf is the correct numerical value. You can check this by:
plot(t, Y)
By the way, vectorization can simplify the code:
function fn = plume5(t,Y, rho, cp)
fn = zeros(8, 1);
fn(1:4) = 1 ./ (rho(1:4)*cp) .* (760.91 - 1608.08 * Y(1:4) + ...
2449.22 * Y(1:4) .^ 2 - 2001.61 * Y(1:4) .^ 3 + ...
904.51 * Y(1:4) .^ 4 - 212.087 * Y(1:4) .^ 5 + 20.095 * Y(1:4) .^6 );
fn(5:6) = 1 ./ (rho(5:8) .* Y(5:8)) * (1.113 - 2.14 * Y(5:8) + ...
2.81 * Y(5:8) .^ 2 - 1.76 * Y(5:8) .^ 3 + 0.396 * Y(5:8) .^ 4 + ...
0.08694 * Y(5:8) .^ 5 - 0.0579 * Y(5:8) .^ 6 + 0.0077 * Y(5:8) .^ 7);
4 Commenti
Jan
il 11 Set 2019
@Sunetra CV: I'm not sure what "scaling down" means here.
@Moumita Ghosh: I cannot follow you. Your comment does not concern the question of this thread, does it? Then please open a new thread and post the details there.
Più risposte (0)
Vedere anche
Categorie
Scopri di più su Loops and Conditional Statements in Help Center e File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!