Extract data from fvtool output

Hi there,

I am designing a filter using MATLAB's Filter Design Tool, however I need to verify certain data points in the response. In particular the group delay values. FVTool allows you to view the results of different responses (e.g. see following image), but I need a means of extracting the response data for further use in my code. How can I extract the group delay (or magnitude and phase) data from the filter design tool?

How can I export that curve?

Thanks for any assistance you can offer me!

Answer 1

[Star Strider]

I don’t routinely use fvtool, so my experience with it is limited. See the section on Modifying the Plot in the fvtool documentation. That will probably let you do what you want.

[Mark Thompson]

Thank you for the suggestion, however I have already looked at that page and I have found no way of exporting the graphed data into a vector that can be later manipulated in the MATLAB workspace.

Is there perhaps a means of generating group delay and frequency response data from the [b,a] coefficients in a MATLAB script (without using the filter design tools) that mean they can be plotted manually later?

[Star Strider]

My pleasure.

You can’t get there from here with fvtool. It’s designed to graphically let you explore the characteristics of your filter in a GUI.

Since you’ve already designed your filter, use the grpdelay, phasedelay, and related functions in the Signal Processing Toolbox to get the results you want.