Unable to iterate my array even though both sides appear to be the same sides.

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Aidan Marrinan 2023-11-21

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评论： Dyuman Joshi 2023-11-25

Hey Im trying to create a series of of notes to play in sucessive order. Every time this runs I get the following error.

"Unable to perform assignment because the left and

right sides have a different number of elements.

Error in DSPLab4>createMusic (line 88)

maxtimes(i) = max(Time{1,i});"

However when I use size(maxtimes) and size(Time) they both are 1x4 so I am not sure why they arent the same size. The code is below:

note_vec = [76, 79, 81, 83];

d_vec = [0,5, 0.5, 0.5, 0.5];

start_vec = [0, 0.5, 1, 1.5];

Test = createMusic(d_vec, note_vec, fs, start_vec);

function music = createMusic(d_vect,note_vect,fs,start_vect)

%the arguments

%d_vect the vector of note durations

%note_vect the vector of note numbers

%fs the sampling frequency

%start_vect the vector of starting times eg [1,0,0] means the first note

%starts after 1 second, while the second and third notes start at 0sec.

for k = 1:1:length(note_vect)

[note,time_note] = createNote(d_vect(k),note_vect(k),fs,start_vect(k));

A{k}=note;

Time{k}=time_note;

end

%check the end of each signal

maxtimes = zeros(1,length(note_vect));

for i=1:length(note_vect)

maxtimes(i) = max(Time{1,i});

end

%append zeros only if necessary to time align the signals

maximus = max(maxtimes);

for i=1:length(note_vect)

A{1,i} = [A{1,i};zeros(ceil(maximus)*fs-ceil(maxtimes(i))*fs,1)];

end

%convert cell to matrix

AlmostThere = zeros(ceil(maximus)*fs,length(note_vect));

for i=1:length(note_vect)

AlmostThere(:,i) = A{1,i};

end

%sum columns of the matrix to get the final music

music = sum(AlmostThere,2);

end

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Florian Bidaud 2023-11-21

Could you share the variable T after looping on k ?

Aidan Marrinan 2023-11-21

Sure I can include the create note function too:

Here after k = 4

Time = 1×4 cell array

{0×1 double} {48000×1 double} {16000×1 double} {16000×1 double}

The create note function below:

function [x,new_t] = createNote(d, note, fs, start) %the note starts after start seconds

f0 = 440*2^((note-69)/12);

N = ceil(d)*fs;

t = (1/fs)*(0:N-1)';

x = sin(2*pi*f0*t);

prep = zeros(start*fs,1);

x = [prep; x];

new_N = ceil(start+d)*fs;

new_t = (1/fs)*(0:new_N-1)';

if note == -1

x = zeros(N,1);

end

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Answer 1

Florian Bidaud 2023-11-21

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2050192-unable-to-iterate-my-array-even-though-both-sides-appear-to-be-the-same-sides#answer_1357207

编辑：Florian Bidaud 2023-11-21

Following your comment, you have the answer,

Time{1} is a 0x1 double, so max(Time{1,1}) is empty, therefore you cannot assign it to maxtimes(1)

The issue comes from the function createNote for k = 1

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Florian Bidaud 2023-11-21

Oops sorry I meant 1, was coding in Python just before answering the question :D

I'm correcting the answer now

Dyuman Joshi 2023-11-25

在 MATLAB Online 中打开

@Aidan Marrinan, The solution is to include a Fail-safe in your code.

for i=1:length(note_vect)
    z = max(Time{1,i});
    %Fail safe
    if isempty(z)
        z=NaN; %Or 0, or any other value you'd like to use as a placeholder
    end
    maxtimes(i) = z;
end

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Unable to iterate my array even though both sides appear to be the same sides.

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