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octave 3.2.4 functions
From: |
john |
Subject: |
octave 3.2.4 functions |
Date: |
Fri, 29 Jul 2011 06:45:16 -0700 (PDT) |
Hi,
I have a problem to run the following programs with functions.It's concern
of solution of a diff.vgl and
eulers method for solving diff.vgl.
function y = rk2a( f, y0, t )
% ----------------------------------------------------------------------
% Jonathan R. Senning <address@hidden>
% Gordon College
% March 22, 1999
%
% Usage: y = rk2a(@f, y0, t)
%
% Returns:
% one-dimensional array of y values associated with the t values
% passed into the function.
%
% Parameters:
% f: handle of function equal to dy/dt.
% y0: y value corresponding to t(1), initial t value
% t: array of points to evaluate solution at
%
% This function implements a 2nd order Runge-Kutta algorithm to solve the
% initial value problem
%
% dy
% -- = f(y,t), y(t_0) = y_0
% dt
%
% This particular version is based on the algorithm presented in
"Numerical
% Analysis", 6th Edition, by Burden and Faires, Brooks-Cole, 1997.
% ----------------------------------------------------------------------
[m, n] = size( t );
y = zeros( m, n );
n = max( m, n );
y(1) = y0;
for i = 1 : n-1
h = t(i+1) - t(i);
k1 = h * f( y(i), t(i) ) / 2.0;
y(i+1) = y(i) + h * f( y(i) + k1, t(i) + h / 2.0 );
end
end
How do I run this program,I tried everything but no result.
----_--second program:
function xdot = f (x, t)
r = k = 1.4;
a = 1.5;
b = 0.16;
c = 0.9;
d = 0.8;
xdot(1) = r*x(1)*(1 - x(1)/k) - a*x(1)*x(2)/(1 + b*x(1));
xdot(2) = c*a*x(1)*x(2)/(1 + b*x(1)) - d*x(2);
endfunction
x0 = [1; 2];
t = linspace (0, 50, 200)';
x = lsode ("f", x0, t);
plot (t, x)
When I save this program as "function xdot" and I type function xdot at the
octave prompt
,no result.
I have a problem to save this functions and to run.
How can I save and run this programs????
Can you help me?
Thank you
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- octave 3.2.4 functions,
john <=