How to Filter Array Based on Values in a Different Array?

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Kelsey Ward 2022-7-19

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https://ww2.mathworks.cn/matlabcentral/answers/1763765-how-to-filter-array-based-on-values-in-a-different-array

回答： Voss 2022-7-19

I have 3 arrays of the same dimensions, and the same indices in these arrays correspond to the same individuals. One array gives the geographic location in latitude of each individual where each row is an individual and each column is a time step and then it gives the latitude at each time step. The 2nd array is the same thing but with longitude. My final array works similarly to give the status of each individual (alive, dead, etc), with the rows representing the same individuals and the columns representing the same time steps and then a numeric value at each index representing the status (-3, -2, -1, 0, or 1).

I want to pull out the locations of certain individuals with a particular status, so I need to pull out all the x and y coordinates from my other 2 arrays based on what number is in the corresponding index of the status array. So for example make new arrays that contain all the x and y coordinates of all alive individuals with status 1, or even better one new array that provides the x and y together for each individual. I have no idea how to even begin this if anyone could point me in the right direction.

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Answer 1

Voss 2022-7-19

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https://ww2.mathworks.cn/matlabcentral/answers/1763765-how-to-filter-array-based-on-values-in-a-different-array#answer_1011080

在 MATLAB Online 中打开

% some random lat/lon/stat matrices
lat = randi([-90 90],5,10)
lat = 5×10
    -7   -28   -33    15   -52   -23    24     5     0    68
    87     0     5   -11   -10    49    47   -65     1   -30
    62   -35   -71    71    -8   -54   -84    15    86    57
    66    32   -13   -31   -10    67   -74   -66    33   -90
    52   -12    63   -76    60   -36   -18   -71    54    74
lon = randi([-180 180],5,10)
lon = 5×10
   173   110   129   -37   152  -132   140   -94   116  -159
   -88   168  -179   -10  -125    -5    13    -2  -101  -147
   -13    16    18  -136    97   -24   -96  -125   156   125
   116     3   134    78   179  -110   108   169  -152   -68
  -142  -131   170   173   -64   -99  -161    34  -169  -117
stat = randi([-3 1],5,10)
stat = 5×10
    -3    -3    -2    -1    -1    -1     1    -1     0     1
    -2     1    -1    -2     0     1     0    -2    -2     1
    -1     0     0     1    -1     1    -3    -1    -3     1
    -2    -3    -3     1     1     0     1    -2    -1    -1
     0    -3    -2     1    -3    -2    -2     0    -3     0
% get the lat and lon where stat == -2
idx = stat == -2;
lat_lon = [lat(idx) lon(idx)]
lat_lon = 10×2
    87   -88
    66   116
   -33   129
    63   170
   -11   -10
   -36   -99
   -18  -161
   -65    -2
   -66   169
     1  -101