Error "undefined function or variable 'y1' ". Help me please. :\

Question

Poison 2014-10-18

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/159150-error-undefined-function-or-variable-y1-help-me-please

评论： Image Analyst 2014-10-28

if true
  % code
end--------------------------------start of the code
clc;
clear all;
Fs=8000;
for k=1:30
  clear y1 y2 y3;
display('record voice');
pause();
x=wavrecord(Fs,Fs);
t=0.04;
j=1;
for i=1:8000
  if(abs(x(i))>t)
      y1(j)=x(i);
      j=j+1;
  end
end
y2=y1/(max(abs(y1)));
y3=[y2,zeros(1,3120-length(y2))];
y=filter([1 -0.9],1,y3');%high pass filter to boost the high frequency components
%%frame blocking
blocklen=240;%30ms block
overlap=80;
block(1,:)=y(1:240);
for i=1:18
  block(i+1,:)=y(i*160:(i*160+blocklen-1));
end
w=hamming(blocklen);
for i=1:19
  a=xcorr((block(i,:).*w'),12);%finding auto correlation from lag -12 to 12
  for j=1:12
      auto(j,:)=fliplr(a(j+1:j+12));%forming autocorrelation matrix from lag 0 to 11
  end
  z=fliplr(a(1:12));%forming a column matrix of autocorrelations for lags 1 to 12
  alpha=pinv(auto)*z';
  lpc(:,i)=alpha;
end
wavplay(x,Fs);
X(k,:)=reshape(lpc,1,228);
Y(k,:)=input('enter the number ');
end
save('lpcdata.mat','X','Y');
---------------------------------------the command
record voice
??? Undefined function or variable 'y1'.

Error in ==> normalizedlpc at 17

y2=y1/(max(abs(y1)));

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Answer 1

Image Analyst 2014-10-18

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/159150-error-undefined-function-or-variable-y1-help-me-please#answer_155683

在 MATLAB Online 中打开

This

j=1;
for i=1:8000
  if(abs(x(i))>t)
      y1(j)=x(i);
      j=j+1;
  end
end

can be vectorized:

y1 = zeros(1, length(x); % Initialize to all zeros.
% Compute logical indexes of where x > t
aboveThreshold = x > t;
if sum(aboveThreshold) > 1
    % At least one element of x is above the threshold.
    % Extract only those above threshold and create a new y1
    % which may be a different length than the initialized one.
    y1 = x(aboveThreshold);
end

but you still might want to find out why no x is above your t threshold, because though my code fixed your code, it will just continue on with a y of all zeros, which is probably useless and not what you want.

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Image Analyst 2014-10-26

The correlation is like you slide and multiply two signals (or the same signal) and sum the result. Normally you slide them the entire way so that the first element is where the right element of the signal on the left overlaps the left element of the signal on the right. They overlap at just that one element. The lag would be the full signal length. Then you slide so that they overlap by two elements. If you want, there is an option to limit the amount of distance they're allowed to be apart (how far away their centers are when they overlap). For example you might know in advance that once the lag (separation) is more than 12 elements, the autocorrelation is basically flat. If the full correlation shows a peak around 0 and after a shift of around 4 or 6 the correlation is essentially zero or a constant, then why go all the way out to the far end? Let's say the signal is 1000 elements long. Why go all the way out to a shift of 1000 elements when all the action is taking place in a shift of less than 12? It will just take longer and not provide any useful information. The 12 is a parameter you can choose based on your experience with that signal. Do the full correlation for some signals and see where all the action takes place and pick your maxLag accordingly.

Poison 2014-10-28

Thank you for the explanation. Meant alot and 1 more question.

Why is my .mat(microsoft access table) files is only a shortcut after i run the program. Is there any way to make in permanently stay in my folder as .mat? And if there isn't, how do i save data into microsoft access table that is open-able afterward?

Thanks in advanced.