I have an array which is increasing. At one point it starts to decrease. This trend starts repeating many times in array. How to extract only the decreasing portion from that array?

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Tez 2017-7-9

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https://ww2.mathworks.cn/matlabcentral/answers/347916-i-have-an-array-which-is-increasing-at-one-point-it-starts-to-decrease-this-trend-starts-repeatin

评论： Walter Roberson 2017-7-25

I have an array which is increasing. At one point it starts to decrease. This trend starts repeating many times in array. How to extract only the decreasing portions from that array and plot another array values which corresponds to that decreasing portion?

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Walter Roberson 2017-7-9

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/347916-i-have-an-array-which-is-increasing-at-one-point-it-starts-to-decrease-this-trend-starts-repeatin#answer_273424

在 MATLAB Online 中打开

d = diff( YourArray(:).' );    %I assume it is a vector of unknown orientation
goes_down = strfind([0 d>0], [1 0]) + 1;
stops_going_down = strfind([0 d<0], [1 0]);
n_seg = length(goes_down);
segs = cell(1, n_seg);
for K = 1 : n_seg;
  segs{K} = YourArray(goes_down(K) : stops_going_down(K));
end

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Tez 2017-7-25

在 MATLAB Online 中打开

How can I apply this code in multiple files?

d = diff( Col3 .' );    %I assume it is a vector of unknown orientation
mask = d < 0;
goes_down = strfind([0 mask], [0 1]) + 1;
stops_going_down = strfind([mask 0], [1 0]) + 1;
n_seg = length(goes_down);
idx2s = cell(1, n_seg);
seg2s = cell(1, n_seg);
seg3s = cell(1, n_seg);
for K = 1 : n_seg
idx2s{K} = goes_down(K) : stops_going_down(K);
seg2s{K} = Col3(idx2s{K});
seg3s{K} = Col2(idx2s{K});
end
segs23 = [seg2s; seg3s];

Walter Roberson 2017-7-25

When you process the multiple files, at each step do you want to forget about the previous file (except perhaps for the plot that has been drawn), or at each step do you want to add on to the seg2s / seg3s arrays so that you end up with one long cell array of those that includes all of the files, or do you want to use a cell array wrapping around each of those so that you can index into the cell array to get the seg2s / seg3s relevant to that file, or ....?

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

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