abs() in anonymous function

Hi there

I solved the previous problem by introducing an anonymous function

f2 = @(t,J) lambda * tau_0 * (0.5*(tanh(J-theta_i)-tanh(-theta_i))) * (0.25*(1-(tanh(-theta_0))^2)) * [ ((1-J)^mu)*(3/2-(3/2-t/tau_0)*(exp(-t/tau_0)))/(tau_p) - 3*alpha*(J^mu)/(tau_m) ] ;

The function "J" appearing in the derivative (f2) is supposed to be "abs(J)" .

All attempts I did ended up with syntax errors..

Thanks in advance :)

Uri

[Geoff Hayes]

Ori - what attempts did you make? What syntax errors did you observe? Why can't you just replace J with abs(J) in your function "body" (leave the input parameter as is)?

[Ori Iger]

I have no idea, but this is the code.

I've tried some solutions of similar problems I found online, with no luck.

Array indices must be positive integers or logical values.

Error in
Model_S1_Weights_Lims>@(t,J)lambda*tau_0*(0.5*(tanh(abs(J(t))-theta_i)-tanh(-theta_i)))*(0.25*(1-(tanh(-theta_0))^2))*[(1-(abs(J(t)))^mu)*(3/2-(3/2-t/tau_0)*(exp(-t/tau_0)))/(tau_p)-3*alpha*((abs(J(t)))^mu)/(tau_m)]
(line 40)
f = @(t,J)   lambda * tau_0 * (0.5*(tanh(abs(J(t)) -theta_i)-tanh(-theta_i)))*(0.25*(1-(tanh(-theta_0))^2)) * [ (1
- (abs(J(t)))^mu) * (3/2-(3/2-t/tau_0) * (exp(-t/tau_0))) /(tau_p) - 3*alpha*((abs(J(t)))^mu) /(tau_m) ];

Error in odearguments (line 90)
f0 = feval(ode,t0,y0,args{:});   % ODE15I sets args{1} to yp0.

Error in ode45 (line 115)
  odearguments(FcnHandlesUsed, solver_name, ode, tspan, y0, options, varargin);

Error in Model_S1_Weights_Lims (line 54)
[t,J]=ode45(f,[0 5000],0.9);

Thanks

Uri

[Ori Iger]

also got this in one attempt

Conversion to logical from symfun is not possible.

[Geoff Hayes]

Ori - you may need to show more of your code so that we can see how the variables to your anonymous function are defined. Are all of the variables scalars? Are any arrays? The error message seems to be telling you that you are trying to use a negative or non-integer index into an array. I do see that you are using square brackets in your code...what is the intention here? Is this valid syntax?

Answer 1

[Steven Lord]

If this error started occurring when you added an abs call inside the anonymous function, you most likely have defined a variable named abs, and your attempts to call the function abs are being interpreted as an attempt to index into the variable abs. Rename or remove the variable, recreate the anonymous function, and call ode45 with the recreated function handle.