Receiving "too many output arguments" error in this code

I am trying to make a effects panel on Matlab App Designer using switch-case logic in order to check which filters are toggled and which are not.

       function applyActiveTransformations(app)
            audio = app.origFXAudioData;
            for i = 1:length(app.activeTransformations)
                switch app.activeTransformations{i}
                    case 'highpass'
                        cutoffFreq = (app.FxFs/2) - 100;
                        normalizedCutoff = cutoffFreq/(app.FxFs/2);
                        [b,a]=butter(4, normalizedCutoff, ...
                            'high');
                        audio = filtfilt(b,a,audio);  
                    case 'lowpass'
                        cutoffFreq = (app.FxFs/2) - 5;
                        [b,a] = butter(4, cutoffFreq / (app.FxFs/2), 'low');
                        audio = filtfilt(b,a,audio) ;
                    case 'bandpass'
                        lowCutoff=(app.FxFs/2) - 10;
                        highCutoff = (app.FxFs/2) - 500;
                        [b,a]= butter(4, [lowCutoff, highCutoff]/(app.FxFs/2),'bandpass');
                        audio = filtfilt(b,a,audio);
                    case 'chipmunk filter'
                        nsemitones = 9;
                        audio = shiftPitch(audio,nsemitones);
                    case 'normalize'
                        audio = audio/max(abs(audio(:)));
                end
            end
            app.procFxAudioData = audio; 
        end

Here is the callback function for one of the filters. The others follow the same logic:

        function highpassButtonPushed(app, event)
        if app.highpassButtonPushed.Value == 1
            app.activeTransformations{end+1} = 'highpass';
        else
            app.activeTransformations = setdiff(app.activeTransformations, {'highpass'},'stable');
        end
        app.applyActiveTransformations();
        end

[Walter Roberson]

Which line is it complaining about, thinking that it has too many outputs ?

[Stephen23]

Please show us the complete error message. That means all of the red text.

[Ria]

Here is the complete error message:

Error using newestAudioProjDec6/highpassButtonPushed

Too many output arguments.

Error in newestAudioProjDec6/highpassButtonPushed (line 1742)

disp(app.highpassButtonPushed.Value)

Error in matlab.apps.AppBase>@(source,event)executeCallback(ams,app,callback,requiresEventData,event) (line 62)

newCallback = @(source, event)executeCallback(ams, ...

Error while evaluating Button PrivateButtonPushedFcn.

[Rik]

That is not the complete message.

[Walter Roberson]

The implication is that somehow app.highpassButtonPushed has become non-scalar, so app.highpassButtonPushed.Value is structure expansion (or object expansion) resulting in multiple parameters passed to disp()

However: the highpassButtonPushed code that you posted does not contain any disp() in it, so either you did not post the correct code or else the wrong version of the code is (somehow) executing.

[Ria]

Here is all of the code related to the FX panel:

properties: 
origFxAudioData
procFxAudioData
FxFs
fxAudioPlayer
activeTransformations


function applyActiveTransformations(app)
disp(app.activeTransformations)
audio = app.origFXAudioData;
for i = 1:length(app.activeTransformations)
    switch app.activeTransformations{i}
        case 'highpass'
            cutoffFreq = (app.FxFs/2) - 100;
            normalizedCutoff = cutoffFreq/(app.FxFs/2);
            [b,a]=butter(4, normalizedCutoff, ...
                'high');
            audio = filtfilt(b,a,audio);
        case 'lowpass'
            cutoffFreq = (app.FxFs/2) - 5;
            [b,a] = butter(4, cutoffFreq / (app.FxFs/2), 'low');
            audio = filtfilt(b,a,audio) ;
        case 'bandpass'
            lowCutoff=(app.FxFs/2) - 10;
            highCutoff = (app.FxFs/2) - 500;
            [b,a]= butter(4, [lowCutoff,                 highCutoff]/(app.FxFs/2),'bandpass');
            audio = filtfilt(b,a,audio);
        case 'chipmunk filter'
            nsemitones = 9;
            audio = shiftPitch(audio,nsemitones);
        case 'normalize'
            audio = audio/max(abs(audio(:)));
    end
end
app.procFxAudioData = audio;     
end

in the startup fnc:

app.activeTransformations = {};

function highpassButtonPushed(app, event)
disp(app.highpassButtonPushed.Value)
disp(app.activeTransformations)
if app.highpassButtonPushed.Value == 1
    app.activeTransformations{end+1} = 'highpass';
else
    app.activeTransformations = setdiff(app.activeTransformations, {'highpass'},'stable');
end
app.applyActiveTransformations();
end
% Button pushed function: lowpassButton
function lowpassButtonPushed(app, event)
if app.lowpassButtonPushed.Value == 1
    app.activeTransformations{end+1} = 'lowpass';
else
    app.activeTransformations = setdiff(app.activeTransformations, {'lowpass'},'stable');
end
app.applyActiveTransformations();

end
% Button pushed function: bandpassButton
function bandpassButtonPushed(app, event)
if app.bandpassButtonPushed.Value == 1
    app.activeTransformations{end+1} = 'bandpass';
else
    app.activeTransformations = setdiff(app.activeTransformations, {'bandpass'},'stable');
end
app.applyActiveTransformations();

end
% Button pushed function: chipmunkfilterButton
function chipmunkfilterButtonPushed(app, event)
if app.chipmunkfilterButtonPushed.Value == 1
    app.activeTransformations{end+1} = 'chipmunk filter';
else
    app.activeTransformations = setdiff(app.activeTransformations, {'chipmunk filter'},'stable');
end
app.applyActiveTransformations();
end
% Button pushed function: normalizeButton
function normalizeButtonPushed(app, event)
if app.normalizeButtonPushed.Value == 1
    app.activeTransformations{end+1} = 'normalize';
else
    app.activeTransformations = setdiff(app.activeTransformations, {'normalize'},'stable');
end
app.applyActiveTransformations();

end

[Walter Roberson]

For the purposes of testing, on the line before

disp(app.highpassButtonPushed.Value)

insert

HIGHBUTTONPUSHED = app.highpassButtonPushed;
whos HIGHBUTTONPUSHED

and tell us what the result is at the time of the error.

[Ria]

here is the error:

Error using riasupdates/highpassButtonPushed

Too many output arguments.

Error in riasupdates/highpassButtonPushed (line 1742)

HIGHBUTTONPUSHED = app.highpassButtonPushed;

Error in matlab.apps.AppBase>@(source,event)executeCallback(ams,app,callback,requiresEventData,event) (line 62)

newCallback = @(source, event)executeCallback(ams, ...

Error while evaluating Button PrivateButtonPushedFcn.

[Walter Roberson]

Hmmm, change

HIGHBUTTONPUSHED = app.highpassButtonPushed;
whos HIGHBUTTONPUSHED

to

whos app event

for testing purposes.

At the moment, it appears that app is non-scalar and might possibly not be an app at all.

[Ria]

here is the new error:

To get started, type doc.

For product information, visit www.mathworks.com.

Name Size Bytes Class Attributes

app 1x1 8 riasupdates

event 1x1 8 matlab.ui.eventdata.ButtonPushedData

Error using riasupdates/highpassButtonPushed

Too many output arguments.

Error in riasupdates/highpassButtonPushed (line 1743)

disp(app.highpassButtonPushed.Value)

Error in matlab.apps.AppBase>@(source,event)executeCallback(ams,app,callback,requiresEventData,event) (line 62)

newCallback = @(source, event)executeCallback(ams, ...

Error while evaluating Button PrivateButtonPushedFcn.

Answer 1

[Walter Roberson]

You define

function highpassButtonPushed(app, event)

which declares highpassButtoPushed as a function that returns no outputs.

You call

disp(app.highpassButtonPushed.Value)

That asks to invoke the function highpassButtonPushed and return some value from that, and index that output at field Value . But highpassButtonPushed is a function that returns no outputs, so the results of it cannot be processed.

You might possibly be wanting to do

disp(app.highpassButton.Value)

[Ria]

When I delete

disp(app.highpassButtonPushed.Value)

I'm still receiving this error.

Error using riasupdates/highpassButtonPushed

Too many output arguments.

Error in riasupdates/highpassButtonPushed (line 1743)

if app.highpassButtonPushed.Value == 1

Error in matlab.apps.AppBase>@(source,event)executeCallback(ams,app,callback,requiresEventData,event) (line 62)

newCallback = @(source, event)executeCallback(ams, ...

Error while evaluating Button PrivateButtonPushedFcn.

[Stephen23]

"I'm still receiving this error."

Because you still have the same bug here:

if app.highpassButtonPushed.Value == 1

which should be replaced with this:

if app.highpassButton.Value == 1