Filter Design Assistant

R2026b

Filter Design Assistant is a tool that opens when you call the designfilt function with invalid or incomplete filter design specifications. The assistant helps you design the filter and displays the corrected MATLAB^® code in the command line.

Open Filter Design Assistant from Command Line

Assume that you have a signal sampled at 2 kHz. You want to design a lowpass FIR filter that suppresses frequency components higher than 650 Hz. To design the filter using these specifications, type this code at the MATLAB command line.

Fsamp = 2e3;
Fctff = 650;
dee = designfilt("lowpassfir",CutoffFrequency=Fctff,SampleRate=Fsamp);

In the dialog box that opens, you can see that the design specifications that the are not valid. Click Yes in the dialog box to use the Filter Design Assistant to design the filter.

In the dialog box that opens, you can see that the Filter Design Assistant has applied the Fsamp and Fctff variables that you created earlier to the corresponding design parameters.

Increase the filter order to 50. Click OK so that Filter Design Assistant can display this code at the command line.

designfilt("lowpassfir",FilterOrder=50,CutoffFrequency=Fctff,SampleRate=Fsamp);

Run this code to design the filter and to save the filter object to the workspace.

Call Filter Analyzer to display the magnitude response plot for the designed filter.

filterAnalyzer(dee)

Based on this frequency response, you can choose to keep this filter or to edit it further using the Filter Designer app. For more information on how to edit the filter in Filter Designer, see Design Filters.

Settings

You can enable or disable the Filter Design Assistant using setpref.

• Use setpref("dontshowmeagain",filterDesignAssistant=false) to enable the assistant. You can also use this command to enable the assistant after disabling it.

• Use setpref("dontshowmeagain",filterDesignAssistant=true) to disable the assistant permanently. You can also select Do not show this message again in the initial dialog box.

Troubleshooting

The designfilt function does not open the Filter Design Assistant, even when you provide invalid design specifications, if:

• You run a code section by clicking Run Section in the Editor or by pressing Ctrl+Enter on a code section. For more information on code sections, see Divide Your File into Sections.

• You execute code from the Live Editor that contains multiple calls to designfilt and at least one of those calls is incorrect.

• You run MATLAB from macOS or Linux^® system prompt with the -nodisplay or -nodesktop options.

• You run designfilt using MATLAB Online™.