topic Re: Need help with plotting column matrix for bode plot in Mathcad

Need help with plotting column matrix for bode plot

AS_9824434 — Mon, 15 Mar 2021 13:12:09 GMT

Hi all,

I hope everyone is having a great day!

I am trying to plot a bode plot(i.e gain in dB w.r.t w in rads-1) at specific frequencies inputted in a vector/matrix.

How then do I plot the column matrix('gaindB') with w(rad s-1) on the horizontal axis?

The transfer function is given by f(s) where s represents laplace constant of j*w

I have attached my workings below.

Re: Need help with plotting column matrix for bode plot

Fred_Kohlhepp — Mon, 15 Mar 2021 13:40:00 GMT

Because gaindB is a vector taking the magnitude results in a scalar. Vectorize:

Re: Need help with plotting column matrix for bode plot

LS_9861888 — Tue, 16 Mar 2021 08:39:56 GMT

The numeric value on the right-hand side of each equation is substituted for the name on the left-hand side in the expressions that define the model. No checking is done during the substitution to determine whether the substituted value is valid.

Re: Need help with plotting column matrix for bode plot

Fred_Kohlhepp — Tue, 16 Mar 2021 11:27:16 GMT

Look up vectorize

Re: Need help with plotting column matrix for bode plot

LucMeekes — Tue, 16 Mar 2021 18:30:08 GMT

Maybe this helps

Success!
Luc

Re: Need help with plotting column matrix for bode plot

Cornel — Tue, 16 Mar 2021 18:41:25 GMT

How to put grid in the graph in Mathcad Prime for Bode Plot (Magnitude & Phase Plot's)?

Or is it only possible if we use a chart component or something like that?

Re: Need help with plotting column matrix for bode plot

LucMeekes — Tue, 16 Mar 2021 21:05:31 GMT

The standard plot of Prime does not come with grids, but there are several methods to put in a grid.

The 3rd party add-on chart-component does provide grids, but it doesn't deal properly with units (as far as I know).

Here's the result of my grid routine

Success!

Luc

Re: Need help with plotting column matrix for bode plot

AS_9824434 — Wed, 17 Mar 2021 13:25:50 GMT

Hi Lucmeekes,

Thanks for that! I am looking at the file you attached.

Can you help me calculate the complex numbers for the specific frequencies in the 'w' vector? The file attached below has wrong values. However, in the bode plot you have plotted does do it correctly, I just need the complex numbers(Re and Im parts) and the gain(screenshot 227). How can I do this, I used vector 'w' but it does not work?

Of course this can be done by pen and paper but that will take too long.

Re: Need help with plotting column matrix for bode plot

LucMeekes — Wed, 17 Mar 2021 14:31:33 GMT

You have to vectorize your expressions (put an arrow above it, look that up in the 'Operators' section on the Math ribbon. It's in the lower-right corner:

I'll leave the phase to you..

The table is easy to reproduce except for the argument at w=0.8. Note that the phase runs on negative continuously, but the argument of a complex number is generally limited to between -pi and pi, or -180 deg and 180 deg.

Success!
Luc

Re: Need help with plotting column matrix for bode plot

Werner_E — Thu, 18 Mar 2021 00:44:31 GMT

@Fred_Kohlhepp

You are replying to a SPAM posting 😉

The text was copied from here: https://de.maplesoft.com/support/help/maple/view.aspx?path=DynamicSystems%2FResponsePlot

The text should look innocent and appropriate for the forum at first glance and when after a while the posting has passed moderation, a SPAM-Link is added. Unfortunately a quite common method which can be seen on other forums as well.

Re: Need help with plotting column matrix for bode plot

Fred_Kohlhepp — Thu, 18 Mar 2021 13:20:39 GMT

@Werner_E

Thanks for the tip!

I rarely chase links in these posts; if there isn't a file attached, or at least a picture, they aren't serious. (And Malwarebytes has been very good at issuing warnings!)

Re: Need help with plotting column matrix for bode plot

AS_9824434 — Thu, 18 Mar 2021 14:06:10 GMT

what sorry?

Re: Need help with plotting column matrix for bode plot

Cornel — Thu, 18 Mar 2021 20:23:24 GMT

Why do we need to vectorize the h transfer function?

Re: Need help with plotting column matrix for bode plot

Cornel — Thu, 18 Mar 2021 20:50:21 GMT

Is it possible to increase the thickness of the numbers on the two axes (values on the x and y axis) in the XY plot? Or this thing is possible just in the Chart Component?

Re: Need help with plotting column matrix for bode plot

LucMeekes — Thu, 18 Mar 2021 20:58:42 GMT

That's not about your post, but the one from LS_9861888.

Luc

Re: Need help with plotting column matrix for bode plot

LucMeekes — Thu, 18 Mar 2021 21:13:15 GMT

We need to vectorize because f is a vector. You're plotting the same transfer function with respect to the variable freq. Now freq is undefined (you didn't define it before the plot) so Prime uses it as an automatic variable, and defines it as a range (that is something different from a vector ! ). While it is handy sometimes for plotting, this automatic variable is not well under your control.

Success!
Luc

Re: Need help with plotting column matrix for bode plot

LucMeekes — Thu, 18 Mar 2021 21:14:13 GMT

So far I have not found any settings to control the axis colour.

Luc