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

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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 ---

Risposta accettata

Dyuman Joshi
Dyuman Joshi il 19 Ott 2023
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})
  5 Commenti
Stephen23
Stephen23 il 20 Ott 2023
Modificato: Stephen23 il 20 Ott 2023
"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
Wynand il 20 Ott 2023
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

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