need help with array resizing

Question

sudipta 2017-1-28

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/322260-need-help-with-array-resizing

编辑： Jan 2017-1-28

ex1245.mat

I am attaching one mat file with my data array. It is a current pulse recorded for negative , positive and zero bias condition. I am trying to resize the collected data by eliminating all values near to zero. I am using the below code for finding slope between every 3 data points and when slope is above certain value detecting that index and select next 60 data points inside loop. But there is some error which I am unable to figure out; causing multiple writing of the selected region. I think I am not able to explain it properly.Here is the code;

k=1;
for i=1:10000
  D(k) = (A1(i+2,2)-A1(i,2))/(A1(i+2,1)-A1(i,1));
  if abs(D(k))>500
      B1(:,k) = A1(i:i+59,2);
      T1(:,k) = A1(i:i+59,1);
      k=k+1;
  end
end
plot(T1,B1,'o-')

Thanks for help.

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Jan 2017-1-28

Please use the "{} code" button to format your code. Thanks. I've done this for you this time.

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Jan 2017-1-28

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/322260-need-help-with-array-resizing#answer_252351

编辑：Jan 2017-1-28

在 MATLAB Online 中打开

A solution with minimal changes:

k = 1;
i = 1;
while i < 9941   % 10000 - 59 because A(i+59, :) is accessed
  D = (A1(i+2,2)-A1(i,2))/(A1(i+2,1)-A1(i,1));  % Is D needed outside?
  if abs(D) > 500
      B1(:,k) = A1(i:i+59,2);
      T1(:,k) = A1(i:i+59,1);
      k = k + 1;
      i = i + 60;   % Exclude the next 59 elements
  else
      i = i + 1
  end
end
plot(T1,B1,'o-');

This will be more efficient:

D     = (A1(3:end, 2) - A1(1:end-2, 2)) ./ (A1(3:end, 1) - A2(1:end-2, 1));
match = find(abs(D > 500));
B1    = zeros(60, numel(match));   % Pre-allocate
T1    = zeros(60, numel(match));   % Pre-allocate
for k = 1:numel(match)
  idx      = match(k);
  T1(:, k) = A1(idx:idx+59, 1);
  B1(:, k) = A1(idx:idx+59, 2);
end