%****************************************************************************
%
%                   CalC version 5.4.0, script "ode.par"
%                     Victor Matveev, January 4, 2005
%
%          Integrate a simple system of ODEs: harmonic oscillator
%
%****************************************************************************

% A system of two ODEs, with initial conditions:

dX/dt =   Y ; X(0) = 0 
dY/dt = - X ; Y(0) = 1 

mode = ODE            % Have to instruct CalC that this is not a PDE system.
Run 10.0              % Integrate the equations for time = 10

% To control time step and accuracy, use the following modification of the above statement:
% Run 10.0 0.01 1e-8  % Same as above, but integrate with dt=0.01 and error tolerance of 1e-8

plot  X          
plot  Y    

% Now, let's also plot the deviation from exact solution:

error.X := X - sin(t) % Notice the syntax: use ":=" for time-dependent auxiliary variable
error.Y := Y - cos(t) % declarations. As you can tell, "." is allowed in variable name.

plot  error.X    % Plot the error variables
plot  error.Y    % If using xmgr, can list several variables in "plot"

plot.print "output."  % Specifies the prefix for file names created for each of the plots

% Uncomment one of the following if running on Linux or SGI platform:

plot.method xmgr
% plot.method gl

% That's it!