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## Re: Parametric system solve -> parametric plot

**From**: |
Ivan Sutoris |

**Subject**: |
Re: Parametric system solve -> parametric plot |

**Date**: |
Sun, 1 Mar 2009 05:38:52 -0800 (PST) |

Bertone wrote:
>* *
>* Hello to everybody,*
>* I'm a physicist and an Octave-proud newbie, I need technical help to solve*
>* a simple problem.*
>* *
>* I've got a parametric nonlinear system of 2 eqns in 2 unknowns plus a*
>* parameter, t:*
>* *
>* f(x,y,t) = 0 AND g(x,y,t) = 0*
>* *
>* well,*
>* *
>* I could solve it point-by-point by setting manually a value for t and*
>* obtaining a point (x(t),y(t)), then following the instructions contained*
>* in the User Manual. *
>* *
>* What should I tell Octave to draw a plot of the curve x(t), y(t) which is*
>* implicitly defined by the system above? *
>* *
>* Thank you all!*
>* *
>* Mario Alberto*
>* *
Hi
if you have already solved your system for various values of t and have the
results in vector x and y, you can just use plot(x,y). Assuming you have
functions f and g already defined, it could look like this (not tested):
t = 0:0.01:1; % or whatever you need
x = zeros(length(t), 1);
y = zeros(length(t), 1);
for i=1:length(t)
solfun = @(X) [f(X(1), X(2), t(i)); g(X(1), X(2), t(i))];
X0 = [1; 1];
X = fsolve(solfun, X0);
x(i) = X(1);
y(i) = X(2);
end
plot(x,y)
BTW, I did not receive your email through regular mailing list (just noticed
it on Nabble), so there may have been some problem with your email passing
through.
Regards
Ivan Sutoris
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