That it really cool!

It got me thinking about whether you can enter arbitrary function which contain arbitrary parameters, like you could for example specify Sin[k x +m] or Sin[k^m * x].

The first problem that arose was that the expression entered was evaluated directly. Using input field, you can specify that the input should be an held expression.

Secondly when I wrote the parameter "o" into my expression ("o" being a parameter that was controlled by manipulate) the expression though I meant the "o" symbol from the global context, rather than the unique "o" created within the manipulate context. I fixed this by renaming the manipulated variable "oval" and since the expression was held, I could replace every instance of Global`o with the unique oval, before releasing the hold.

Manipulate[
 Dynamic[
  Plot[ReleaseHold[ReplaceAll[f, {o -> oval, p -> pval}]], {x, -5, 5}]
  ],
 {{oval, 1, "o"}, 1, 10},
 {{pval, 2, "p"}, 2, 10},
 {{f, Hold[Sin[o x + p]]}, InputField[Dynamic[f], Hold[Expression]] &}]

Cheers!

Hi!

You could add a button that when pressed, assigns the plot expression to a variable:

Manipulate[
 Column[{Button["Calculate", 
    plot = Plot[
      ReleaseHold[ReplaceAll[f, {o -> oval, p -> pval}]], {x, -5, 5}]],
   Dynamic[plot]}], {{oval, 1, "o"}, 1, 10}, {{pval, 2, "p"}, 2, 
  10}, {{f, Hold[Sin[o x + p]]}, 
  InputField[Dynamic[f], Hold[Expression]] &}, {{plot, 
   Plot[Sin[1 x + 2], {x, -5, 5}]}, None }
 ]

plot is a dynamic variable inside manipulate, but since I specified "None", it does not have a control associated with it.

I realized what causes the problem in your original code:

Manipulate[DynamicModule[{f = Sin[o x + p]}, 
Column[{InputField[Dynamic[f]], Dynamic[Plot[f, {x, -5, 5}]]}]], {o,1, 10}, { p, 2, 10}]

Since o and p are tracked by manipulate, any changes to them will reevaluate expressions inside of it. This includes the assignment f=Sin[o x +p] in DynamicModule. In fact, I think the whole dynamic module will be re-instanced.

This is really nice it will help me a lot. Let me ask you couple of things (I appreciate your help)

In your code you o with oval and p with pval because you are using hold? Do you know away of doing it with a calculate button? As in the code will wait for that push button or a tick in order to make the calculation?

I believe there is at least for Enterprise CDF which I use but to be honest documentation is not as good as MATLAB.

Thanks for the reply. I can live with that to learn something but eventually I need more complex inputs. I am trying to develop apps for scientific calculations where I need to have a input field that the user can enter a function of his desire with desired values of the variables not limited sliders.