error,defined variable seems to be undefined

[Idomeneas Pateros]

Hello
I use octave version 3.0.1 on Ubuntu 9.04 Linux platform and when I run the function :

SolveDuffing (see files in attachment)

in command prompt I receive the error :

error: `t' undefined near line 3 column 8
error: evaluating argument list element number 1
error: called from `resultsplot' in file `/home/idomeneas/OctaveProjects/DuffingEquation.dir/resultsplot.m'
error: called from `SolveDuffing' in file `/home/idomeneas/OctaveProjects/DuffingEquation.dir/SolveDuffing.m'

The problem seems to be in calling the function in resultsplot.m file, but when I copy the commands from resultsplot.m to SolveDuffing.m
and run the SolveDuffing, the plots are correct.

I appreciate any help about this problem.

Thank you
 
Idomeneas


[SolveDuffing.m]

---

function SolveDuffing
clear
disp('Solving Duffing for different initial conditions')
xo=0.;vo=0.;eps=1E-3;
x0=[xo;xo+eps;xo+10.*eps];
v0=[vo;vo+eps;vo+10.*eps];
t=linspace(0.,100.,1000.);
x=lsode("Duffing",[x0(1);v0(1)],t);
y=lsode("Duffing",[x0(2);v0(2)],t);
z=lsode("Duffing",[x0(3);v0(3)],t);
resultsplot
%  figure(1)
%  plot(t,x(:,1),'b',t,x(:,2),'r')
%  xlabel("t")
%  ylabel("dx/dt")
%  figure(2)
%  plot(t,y(:,1),'b',t,y(:,2),'r')
%  xlabel("t")
%  ylabel("dx/dt")
%  figure(3)
%  plot(t,z(:,1),'b',t,z(:,2),'r')
%  xlabel("t")
%  ylabel("dx/dt")
endfunction

---

[resultsplot.m]

---

function resultsplot
  figure(1)
  plot(t,x(:,1),'b',t,x(:,2),'r')
  xlabel("t")
  ylabel("dx/dt")
  figure(2)
  plot(t,y(:,1),'b',t,y(:,2),'r')
  xlabel("t")
  ylabel("dx/dt")
  figure(3)
  plot(t,z(:,1),'b',t,z(:,2),'r')
  xlabel("t")
  ylabel("dx/dt")
endfunction

---

[Duffing.m]

---

%Duffing's Equation
function xdot = Duffing (x,t)
  omega=3.5;
  F=0.85;
  xdot(1) = x(2);
  xdot(2) = -x(2) + 10.*x(1)-100.*x(1)*x(1)*x(1)+F*cos(omega*t);
endfunction

---

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[John W. Eaton-3]

On 29-Oct-2009, Idomeneas Pateros wrote:

| Hello
| I use octave version 3.0.1 on Ubuntu 9.04 Linux platform and when I run the
| function :
|
| SolveDuffing (see files in attachment)
|
| in command prompt I receive the error :
|
| error: `t' undefined near line 3 column 8
| error: evaluating argument list element number 1
| error: called from `resultsplot' in file
| `/home/idomeneas/OctaveProjects/DuffingEquation.dir/resultsplot.m'
| error: called from `SolveDuffing' in file
| `/home/idomeneas/OctaveProjects/DuffingEquation.dir/SolveDuffing.m'
|
| The problem seems to be in calling the function in resultsplot.m file, but
| when I copy the commands from resultsplot.m to SolveDuffing.m
| and run the SolveDuffing, the plots are correct.
|
| I appreciate any help about this problem.

This doesn't look like a bug in Octave.  Your resultplot function
doesn't have any arguments, so t (and x) will be undefined inside that
function.

| function resultsplot
|   figure(1)
|   plot(t,x(:,1),'b',t,x(:,2),'r')
|   xlabel("t")
|   ylabel("dx/dt")
|   figure(2)
|   plot(t,y(:,1),'b',t,y(:,2),'r')
|   xlabel("t")
|   ylabel("dx/dt")
|   figure(3)
|   plot(t,z(:,1),'b',t,z(:,2),'r')
|   xlabel("t")
|   ylabel("dx/dt")
| endfunction

Write this as

  function resultplot (x, t)

and then call it with

  resultplot (x, t)

and it should work.

Unless you have a bug to report, please use the help list.

jwe
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[Idomeneas Pateros]

I tried to remove the function and the endfunction commands and the program worked because the t,x,y,z variables were already defined in the SolveDuffing function.

John W. Eaton-3 wrote:

On 29-Oct-2009, Idomeneas Pateros wrote:

| Hello
| I use octave version 3.0.1 on Ubuntu 9.04 Linux platform and when I run the
| function :
|
| SolveDuffing (see files in attachment)
|
| in command prompt I receive the error :
|
| error: `t' undefined near line 3 column 8
| error: evaluating argument list element number 1
| error: called from `resultsplot' in file
| `/home/idomeneas/OctaveProjects/DuffingEquation.dir/resultsplot.m'
| error: called from `SolveDuffing' in file
| `/home/idomeneas/OctaveProjects/DuffingEquation.dir/SolveDuffing.m'
|
| The problem seems to be in calling the function in resultsplot.m file, but
| when I copy the commands from resultsplot.m to SolveDuffing.m
| and run the SolveDuffing, the plots are correct.
|
| I appreciate any help about this problem.

This doesn't look like a bug in Octave.  Your resultplot function
doesn't have any arguments, so t (and x) will be undefined inside that
function.

| function resultsplot
|   figure(1)
|   plot(t,x(:,1),'b',t,x(:,2),'r')
|   xlabel("t")
|   ylabel("dx/dt")
|   figure(2)
|   plot(t,y(:,1),'b',t,y(:,2),'r')
|   xlabel("t")
|   ylabel("dx/dt")
|   figure(3)
|   plot(t,z(:,1),'b',t,z(:,2),'r')
|   xlabel("t")
|   ylabel("dx/dt")
| endfunction

Write this as

  function resultplot (x, t)

and then call it with

  resultplot (x, t)

and it should work.

Unless you have a bug to report, please use the help list.

jwe
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