MATLAB: Remove rows under certain condition

MATLABremove rows under certain condition

Can you help?

On below matrix, for same X and Y, pick smallest Z, then put into a new matrix.

X Y Z 60,-40,1.1 55,-40,3.1 55,-45,4.5 60,-45,5.3 60,-40,7 55,-40,8.4 55,-45,9.8 60,-40,11.2 60,-45,12.6 55,-40,14 55,-45,15.4 60,-45,16.8 60,-40,18.2 60,-45,19.6 55,-40,21 60,-40,22.4 55,-45,23.8 60,-45,25.2 55,-40,26.6 55,-45,28

Best Answer

Assuming your X, Y, and Z variables are stored in three vectors of equal length

[UniqueXY, ~, k] = unique([X(:) Y(:)],'rows') ;
MinZ = accumarray(k, Z(:), [], @min)

Related Solutions

MATLAB: Create matrix with periodic increments

The function bsxfun is really handy for these kind of tasks:

>> X = [1;2;3;4;5;6];
>> Y = bsxfun(@plus,X,0:10:40);
>> Z = bsxfun(@plus,Y(:),0:20);
>> Z
Z =
    1    2    3    4    5    6    7    8    9   10   11   12   13   14   15   16   17   18   19   20   21
    2    3    4    5    6    7    8    9   10   11   12   13   14   15   16   17   18   19   20   21   22
    3    4    5    6    7    8    9   10   11   12   13   14   15   16   17   18   19   20   21   22   23
    4    5    6    7    8    9   10   11   12   13   14   15   16   17   18   19   20   21   22   23   24
    5    6    7    8    9   10   11   12   13   14   15   16   17   18   19   20   21   22   23   24   25
    6    7    8    9   10   11   12   13   14   15   16   17   18   19   20   21   22   23   24   25   26
   11   12   13   14   15   16   17   18   19   20   21   22   23   24   25   26   27   28   29   30   31
   12   13   14   15   16   17   18   19   20   21   22   23   24   25   26   27   28   29   30   31   32
   13   14   15   16   17   18   19   20   21   22   23   24   25   26   27   28   29   30   31   32   33
   14   15   16   17   18   19   20   21   22   23   24   25   26   27   28   29   30   31   32   33   34
   15   16   17   18   19   20   21   22   23   24   25   26   27   28   29   30   31   32   33   34   35
   16   17   18   19   20   21   22   23   24   25   26   27   28   29   30   31   32   33   34   35   36
   21   22   23   24   25   26   27   28   29   30   31   32   33   34   35   36   37   38   39   40   41
   22   23   24   25   26   27   28   29   30   31   32   33   34   35   36   37   38   39   40   41   42
   23   24   25   26   27   28   29   30   31   32   33   34   35   36   37   38   39   40   41   42   43
   24   25   26   27   28   29   30   31   32   33   34   35   36   37   38   39   40   41   42   43   44
   25   26   27   28   29   30   31   32   33   34   35   36   37   38   39   40   41   42   43   44   45
   26   27   28   29   30   31   32   33   34   35   36   37   38   39   40   41   42   43   44   45   46
   31   32   33   34   35   36   37   38   39   40   41   42   43   44   45   46   47   48   49   50   51
   32   33   34   35   36   37   38   39   40   41   42   43   44   45   46   47   48   49   50   51   52
   33   34   35   36   37   38   39   40   41   42   43   44   45   46   47   48   49   50   51   52   53
   34   35   36   37   38   39   40   41   42   43   44   45   46   47   48   49   50   51   52   53   54
   35   36   37   38   39   40   41   42   43   44   45   46   47   48   49   50   51   52   53   54   55
   36   37   38   39   40   41   42   43   44   45   46   47   48   49   50   51   52   53   54   55   56
   41   42   43   44   45   46   47   48   49   50   51   52   53   54   55   56   57   58   59   60   61
   42   43   44   45   46   47   48   49   50   51   52   53   54   55   56   57   58   59   60   61   62
   43   44   45   46   47   48   49   50   51   52   53   54   55   56   57   58   59   60   61   62   63
   44   45   46   47   48   49   50   51   52   53   54   55   56   57   58   59   60   61   62   63   64
   45   46   47   48   49   50   51   52   53   54   55   56   57   58   59   60   61   62   63   64   65
   46   47   48   49   50   51   52   53   54   55   56   57   58   59   60   61   62   63   64   65   66

MATLAB: Remove rows by pick the min value in another column

x=[55,-45,9.8 
60,-40,11.2 
60,-45,12.6 
55,-40,14 
55,-45,15.4 
60,-45,16.8 
60,-40,18.2 
60,-45,19.6 
55,-40,21 
60,-40,22.4 
55,-45,23.8 
60,-45,25.2 
55,-40,26.6 
55,-45,28]
[a,~,c] = unique(x(:,1:2),'rows');
n = size(a,1);
valuemin = zeros(n,4);
for ii = 1:n
    i0 = find(c == ii);
    [valuemin(ii,3),i1] = min(x(i0,end));
    valuemin(ii,[1:2,4]) = [a(ii,:),i0(i1)];
end

[a,~,c] = unique(x(:,1:2),'rows');
idx = accumarray(c,(1:size(x,1))',[],@(y)y(min(x(y,3))==x(y,3)));
valuemin = [a,x(idx,3),idx];

Best Answer

Related Solutions

MATLAB: Create matrix with periodic increments

MATLAB: Remove rows by pick the min value in another column

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