Find the specific data point from array or matrix

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Rahul Panchal 2016-10-21

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https://ww2.mathworks.cn/matlabcentral/answers/308530-find-the-specific-data-point-from-array-or-matrix

编辑： James Tursa 2016-10-21

Hi,

I have a data set with number of acquired signals. Where first column represents the time. and other columns are the acquired signals like pressures, temperature with 200 data point per second rate for molding process. There are over 300 data files which I am scanning through to find specific time for specific data trend/ or change. If I plot the pressure curve I am interested in will look like as attached image. Here I am trying to find the point 'packing end' which should be on the flat line at 13000 psi (the pressure will vary for different cycle). The "packing end" will give the end of certain process stage where pressure will suddenly change to almost zero( see figure - marked with blue oval and green *) but I use the diff and find function for data point from "Peak pressure" or "Max packing" to the length of the array, it gives "packing end" at origin or zero time.

------------my code------

a = length(xxRJG)
iPMax_MP= min(find(xxRJG(:,3)==max(xxRJG(:,3))))
    PMax_MP = xxRJG(iPMax_MP,3) % peak injection pressure (machine)%%also considered as end of fill
iPStart_MP=max(find(xxRJG(1:200,3)<1000))
    PStart_MP = xxRJG(iPStart_MP,3) % filling start
iPPack_MP = max(find(xxRJG((iPMax_MP+100:iPMax_MP+350),3)))%==max((xxRJG((iPMax_MP+100:iPMax_MP+1000),3))))
    PPack_MP = xxRJG(iPPack_MP,3)% packing pressure
           PPack= 0.0*PPack_MP+5.95 % finding the thresold difference to find the end of packing
      iPPack_End = find(diff(xxRJG(iPPack_MP:iPPack_MP+1250,3)),1, 'first'); % finding end of packing point
    PPack_End = xxRJG(iPPack_End,1) % time at end of packing