Using Mathematica Manipulate function to plot a transfer function

Question

It's my first time asking for help here, I hope someone respond. I was hoping to post images to show the problem I had but I need at least 10 reps to do it. But I hope everyone understand what I'm asking for.

I'm trying to create a manipulate box to plot a transfer function with type in boxes so that I can type in the the transfer function and specify the x and y axis. But the plot itself is not appearing only the axis are

but if i type the code outside of "manipulate" it works.

If you try running this on Mathematica you could probably see the problem I'm having.

My mathematica code is below.

Manipulate[tfplot,


 {{tfplot1, 0, "Transfer Function="}},


Delimiter,

 {{fmin1, 10, "fmin = "}},
 {{fmax1, 10^7, "fmax = "}},
 {{ymin1, 1, "ymin = "}},
 {{ymax1, 2*10^2, "ymax = "}},


 Delimiter,
 Row[{

   Button["Plot", tfplot = LogLogPlot[Abs[tfplot2[2*Pi*I*f] /. {tfplot2[s_] -> tfplot1}], {f, fmin1, fmax1}, PlotPoints -> 1000, PlotRange -> {{fmin1, fmax1}, {ymin1, ymax1}}, PlotLabel -> "tf Plot"], ImageSize -> 80] 
}]

 , ControlPlacement -> {Left, Left, Left, Left, Left, Left, Left, Top}]

tfplot3 = (3.333321894500285`*^6 (4.611679331492357`*^6 - 72057.48955456808` s - 4.138291871540356`*^9 s^3 - 3.889993968666704`*^9 s^4 + s^5))/(s^2 (2.606152799059127`*^18 + 4.6278171788297256`*^16 s + 1.0779994813998577`*^14 s^2 + 1.5235290577558628`*^8 s^3 + s^4))

LogLogPlot[Abs[tfplot4[2*Pi*I*f] /. {tfplot4[s_] -> tfplot3}], {f, 10, 10^7}, PlotPoints -> 1000, PlotRange -> {{10, 10^7}, {1, 2*10^2}}, PlotLabel -> "tf Plot"]

Thank you.

Spiderfiq

You should take this to mathematica.stackexchange.com. One thing, you do not (should not) need the plot button, if you get it right the plot will auto update on its own. (that's what manputlate does..). Your fundamental problem though is that keying in an expression as a manipulate variable doesnt seem to work. — agentp
Perhaps SingularValuePlot and TransferFunctionModel are more straightforward? — Rojo

agentp agentp · Accepted Answer · 2013-10-17T18:17:51

Edit .. take 2..

Manipulate[
        fplot = LogLogPlot[Abs[tfplotf /. s -> 2*Pi*I*f], {f, fmin1, fmax1}, 
           PlotPoints -> 1000, PlotRange -> {{fmin1, fmax1}, {ymin1, ymax1}}, 
           PlotLabel -> "tf Plot"],
         {{tfplotf, (3.333321894500285`*^6 (4.611679331492357`*^6 - 
                72057.48955456808` s - 4.138291871540356`*^9 s^3 - 
                3.889993968666704`*^9 s^4 + 
                s^5))/(s^2 (2.606152799059127`*^18 + 
                4.6278171788297256`*^16 s + 1.0779994813998577`*^14 s^2 + 
                1.5235290577558628`*^8 s^3 + s^4))
           , "Transfer Function="}},
    Delimiter,
        {{fmin1, 10, "fmin = "}},
        {{fmax1, 10^7, "fmax = "}},
        {{ymin1, 1, "ymin = "}},
        {{ymax1, 2*10^2, "ymax = "}},
    Delimiter,
         ControlPlacement -> {Left, Left, Left, Left, Left, Left, Left, Top}]

Using Mathematica Manipulate function to plot a transfer function

2 Answers