Finding area of a plot/graph in a for loop and save answer into array

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whalelady 2020-4-16

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/518254-finding-area-of-a-plot-graph-in-a-for-loop-and-save-answer-into-array

评论： Walter Roberson 2020-4-16

采纳的回答： Geoff Hayes

在 MATLAB Online 中打开

Hello Community,

I have a few audio files.

When I open one of these files, I have a file named 'data' in my workspace which contains the data set to plot it's graph.

I am trying to get the area of every audio file in a loop, and save it in an array in a column.

Is anyone able to help with my code especially on : [data,fs] = audioread(Extracted_files(k).name);

I am running into errors for this particular line.

note that every graph is different..

A = zeros(210,1); %set array for allocating the area of 210 of these audio files
m=1;
cd 'my directory'
Extracted_files = dir;
nExtracted_files = length(Extracted_files);
for k = 1:nExtracted_files
    [data,fs] = audioread(Extracted_files(k).name);
    area = trapz(data)
    A(m) = area;
    m = m + 1;
end

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Walter Roberson 2020-4-16

http://matlab.wikia.com/wiki/FAQ#How_can_I_process_a_sequence_of_files.3F

Walter Roberson 2020-4-16

在 MATLAB Online 中打开

plot (data)

Before you do that, you have to read from the file indicated by Extracted_files(k).name

area = trapz(x,y) %or should I use area(x,y)?

Your code does not define x or y, so ... ?

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Answer 1

Geoff Hayes 2020-4-16

1
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/518254-finding-area-of-a-plot-graph-in-a-for-loop-and-save-answer-into-array#answer_426321

在 MATLAB Online 中打开

whalelady - you mention that you are running into errors with

data,fs] = audioread(Extracted_files(k).name);

but you don't mention what the errors are. Is it

Error using audioread (line 74)
The filename specified was not found in the MATLAB path.

? When you call dir, some unexpected "files" may be added to your list (perhaps "." or ".."). I recommend that you add a filter like

Extracted_files = dir('*.wav');

or whatever extension makes sense for your files. Also, there is no need for the m variable as k can be used in its place. Your code could look like

cd 'my directory'
Extracted_files = dir('*.wav');
nExtracted_files = length(Extracted_files);
A = zeros(nExtracted_files,1);
for k = 1:nExtracted_files
    [data,fs] = audioread(Extracted_files(k).name);
    area = trapz(data)
    A(k) = area;
end