Error using 'splitapply' when the first bin has no entries

I am writing a function to take the values from a cell array, split them according the the values in the second column of each cell and then get the average for each cell.

I am running into an issue where in one of the instances the first bin has no values that go in it and then I get this issue

Error using splitapply (line 111)

For N groups, every integer between 1 and N must occur at least once in the vector of group numbers.

I have looked around at old question but am unable to find a solution to my problem.

Note 1 - A function that returns an (:,2) array. The first column contained amplitudes to frequency spikes

Note 2 - The location the error occurs at

Thank you

%function z = Band_Divider(Frequencies, band_width)

% --- TEST SETUP ---
clear;
x = audioread("Recordings\Speaker Male\2\21.wav");
Frequencies = FFT_Output(x, 2, 5);                      %% NOTE 1   This function takes an audio signal and identifies the peak frequencies per word section. The frequencies are stored in a cell 
band_width = 30;
% --- END ---

% --- SETUP ---
Word_Breakdown = zeros(4,(300/band_width));
bins = 0:(band_width):300;

% --- LOOP ---
for i=1:4
    array = Frequencies{i}
    Seperators = discretize(array(:,2), bins)
    Bands = splitapply(@(x) {x}, array, Seperators)         % NOTE 2   The error occurs at this line
    for j=1:height(Bands)
        Band_Value = Bands{j}(:,1)
        Word_Breakdown(i,j) = mean(Band_Value);
    end
end
%end


%--- TEST PRINTS ---
Word_Breakdown
%--- END ---

Answer 1

[Dyuman Joshi]

That is a limitation (for the lack of a better word) of splitapply.

Please try this method with accumarray -

array = Frequencies{i};
Seperators = discretize(array(:,2), bins);
Bands = accumarray(Seperators, array, [], @(x) {x})

[Wynand]

Thank you for the answer. This returns some errors of it's own but I will try to fix them myself first

[Dyuman Joshi]

You are welcome!

You can ask any follow up questions you have here, I'll be happy to assist you with them.

[Wynand]

Thank you. Sorry for bothering you so much with this question but I can't seem to resolve the new error either.

This is the code

% function z = Band_Divider(Frequencies, band_width)

% --- TEST SETUP ---
clear;
x = audioread("Recordings\Speaker Male\1\11.wav");
Frequencies = FFT_Output(x, 2, 5);
band_width = 30;
% --- END ---

% --- SETUP ---
Word_Breakdown = zeros(4,(300/band_width));
bins = 0:(band_width):300;

% --- LOOP ---

array = Frequencies{1}
Seperators = discretize(array(:,2), bins)
Bands = accumarray(Seperators, array, [], @(x) {x})



% end


%--- TEST PRINTS ---
Word_Breakdown;
%--- END ---

This is my variable values and the final part is the error code I get

array = 10×2

0.0438 6.0000

0.0560 14.0000

0.1153 20.0000

0.0303 27.0000

0.0777 33.0000

0.1642 39.0000

0.0381 47.0000

0.0239 54.0000

0.0223 62.0000

0.0139 72.0000

Seperators = 10×1

1

1

1

1

2

2

2

2

3

3

Error using accumarray

Second input VAL must be a vector with one element for each row in SUBS, or a scalar.

[Stephen23]

"Second input VAL must be a vector with one element for each row in SUBS, or a scalar."

Is your 2nd input a vector or a scalar? (hint: no)

I am guessing that you intended to only input the first column of ARRAY:

accumarray(Seperators, array(:,1), [], @(x) {x})

Is there a good reason why you don't simply calculate the mean directly?:

accumarray(Seperators, array(:,1), [], @mean)

[Wynand]

I was inteding to use only the first column yes, that was a oversight on my part.

There isn't no. Mostly a lack of understanding the function and documentation.

Thank you for the help. Implementing your new hints did solve this issue. On to the next