Using time t as a input in functions?

[Wei, Jingjin]

Hi dynasim users,

I was trying to use time t in a custom function, but it seems that it doesn't work. Code is like:

output_value = function(t);

And the function could simply be output = input, so it's not about a bug in the function.

Error saying Undefined function or variable 't'.

My question is does dynasim not allow this, and is the workaround putting t related variable in the final equation, not in a separate line using a custom function?

Best,

Jingjin

[Erik Roberts]

IIRC there’s 2 options, depending on if you want the whole time vector at once (option 1), or the individual time points (option 2)

1)

```

output_value = function(T)

```

or

2)

```

output_value(t) = function(t)

```

-Erik

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[Wei, Jingjin]

Hi Erik,

I tried option 2, 'Index exceeds matrix dimensions'. Well the output here is a scaler, so the error message makes sense since in output(t) t is treated as a index.

Best,

Jingjin

---

From: dynasi...@googlegroups.com <dynasi...@googlegroups.com> on behalf of Erik Roberts <erobe...@gmail.com>
Sent: Monday, May 6, 2019 5:29 PM
To: Wei, Jingjin
Cc: DynaSim Users
Subject: Re: [DS] Using time t as a input in functions?

 

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[Jason Sherfey]

Hi Jingjin,

I'm not totally sure what you're trying to do, but here are some tips on how dynasim treats some time variables:

• "T" will be replaced by the complete time vector computed before simulation.
  
• "t" will be replaced at each time step during integration by the current time (a scalar value in milliseconds).
• "k" will be replaced at each time step during integration by an index value for the current time step.

For instance:

Using the k index:

input = get_input(options); % obtain input vector for the entire simulation (before integration begins)

dV/dt = input(k) + ...; % obtain the k-th value of the input vector during the k-th integration step

Using the t variable:

input(t) = sin(2*pi*t/1e3); % obtain scalar input value at a given time point "t"

dV/dt = input(t) + ...; 

Hope this helps.

Cheers,

Jason

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[Wei, Jingjin]

Hi Jason,

I forgot to reply all, it was solved. Thanks!

Best,

Jingjin

---

From: dynasi...@googlegroups.com <dynasi...@googlegroups.com> on behalf of Jason Sherfey <jssh...@gmail.com>
Sent: Monday, May 6, 2019 7:08 PM
To: Wei, Jingjin
Cc: Erik Roberts; DynaSim Users

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