Input argument "y" is undefined.

Hi

I am using the ode45 and I have been have one error message which I have tried to get get rid of but it still keeps coming up.

Input argument "y" is undefined.

Error in ==> trombe11 at 14
Tf1 =((y-b)-s1/Uc)*exp(-Ac*Uc*F/(m*cp))+(b+s1/Uc);

My m file program is:

 function [dy] = trombe11(t,y )
  Ac=0.2014;
  Ar=2.2;
  Aw=0.32;
  Uc=3.1;
  Uw=5.68;
  Ut=1.03;
  rho=1.23;
  m =0.01353;
  cp=1.003;
  F=0.83;
  b=8;
  s1=15.68;
  Tf1 =((y-b)-s1/Uc)*exp(-Ac*Uc*F/(m*cp))+(b+s1/Uc);
  dy(1)=((Tf1-y)*0.011)/3.96 -((Ut*Ar+Uw*Aw)*(y-b)/(rho*cp*3.96));

The y value is the only parameter which is changing all the others are constants.

I also get a ~ sign on the t on the first line.

my ode function on the command space is:

>> yo=15;
>> tspan=[0:1:4];
>> [t,y]=ode45(@trombe11,tspan,yo);
>> plot(t,y);

The graph which I get is wrong.

Can anyone please suggest to me what I could do to eliminate this error.

Any help will be much appreciated

[Walter Roberson]

Could you explain further about "I also get a ~ sign on the t on the first line." ??

Answer 1

[Wayne King]

I have no problem running this code:

 yo=15; 
 tspan=[0:1:4];
 [t,y]=ode45(@trombe11,tspan,yo);
 plot(t,y)

Make sure that trombe11.m is saved in a folder that is on your MATLAB path. If you have it saved in c:\mfiles for example, then use

   >>addpath 'c:\mfiles'

or the

    >>pathtool

to add the folder.

As far as the plot not being correct, I don't know how we can address that without more details about what you expect to see.

[Walter Roberson]

Nimco replied,

Thank you for your help, I saved my work on MATLAB folder, but not MATLAB path. Are they the same thing?

I get the error reading when I press the publish icon in the m file but the program still runs.

m file

function [dy] = trombe11(t,y )
Ac=0.2014;
Ar=2.2;
Aw=0.32;
Uc=3.1;
Uw=5.68;
Ut=1.03;
rho=1.23;
m =0.01353;
cp=1.003;
F=0.83;
b=8;
s1=15.68;
Tf1 =((y-b)-s1/Uc)*exp(-Ac*Uc*F/(m*cp))+(b+s1/Uc);
dy(1)=((Tf1-y)*0.011)/3.96 -((Ut*Ar+Uw*Aw)*(y-b)/(rho*cp*3.96));

Input argument "y" is undefined.

Error in ==> trombe11 at 14
Tf1 =((y-b)-s1/Uc)*exp(-Ac*Uc*F/(m*cp))+(b+s1/Uc);

Command space 
>> yo=15;
>> tspan=[0:1:4];
>> [t,y]=ode45(@trombe11,tspan,yo);
>> plot(t,y);

When I call the ode, I get a graph where y comes down with increasing time, but I am looking for the graph where y values increase with time.

Can anyone please suggest to me, what I could do solve this problem

[Walter Roberson]

Don't press the "publish" icon!