how can i calculate the rms of a vector ?

Question

Mallouli Marwa 2016-5-3

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评论： Camille Dingam 2020-3-10

my problem consist to calculate the rms of v using for loop. But this for loop display vrms as zeros

for i=1:2500
vs=sum((v(i,1))^2)
end
vrms=sqrt((1/2501)*vs);

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Answer 1

Guillaume 2016-5-3

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You get 0 because the last value in v is 0 and your vs is just the last value of v squared. Notice that sum(v(i)) is just v(i). You probably meant:

vs = vs + v(i)^2;

Your loop is badly constructed by the way. For a start you shouldn't hardcode the length of the vector, you can get it with numel. You also shouldn't use subscript indexing when linear indexing suffices. That way, it would work with row or column vectors:

vs = 0;
for i = 1:numel(v)
  vs = vs + v(i)^2;
end
vrms = sqrt(vs / (numel(v)+1));

In any case, the loop is completely unnecessary:

vs = sum(v.^2);
vrms = sqrt(vs / (numel(v)+1));

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Mallouli Marwa 2016-5-3

thank's a lot

Tahariet Sharon 2017-11-25

编辑：Tahariet Sharon 2017-11-25

why do you divide by plus 1?

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Answer 2

Star Strider 2016-5-3

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The root-mean-square calculation is a one-line calculation:

v = sin([1:0.1:20]*2*pi);                           % Create Data
rms = sqrt(mean(v.^2));

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Star Strider 2016-5-4

My pleasure.

Camille Dingam 2020-3-10

I have done the work with normal people and dysarthria(sick person) audio datasets. I have extracted the rms(root mean squared) energies of their vowels, and i found that dysarthria rms energies of the vowels are mostly high than normal person, please i try to make a conclusion of it. If anyone have some ideas of rms energy, can you tell me why the vowels rms energies are high in dysarthria? Thank you for your reply

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