MATLAB: Method to count number of observations by category

countMATLAB

What would be the best method to count observations which fit the criteria number listed in the last column:
>> s
s =
     22.9924   46.8888    1.4597    4.8547    1.3379    3.8795   24.8686    3.0000
     19.7965   40.1072    1.4644    5.2458    1.3262    3.0253   19.7573    3.0000
     12.0315   70.3394    1.8392    3.6708    1.2664    2.2959   13.2066    3.0000
      0.0854    4.4000    1.3399    1.6076    1.2214    1.9499    1.7144    2.0000
    -10.7796   26.7116    1.0871    1.0044    1.2722    1.6683  -12.4818    1.0000
      1.3617   15.7695    1.0896    1.4550    1.2444    1.9098    1.2284    2.0000
     14.2101   11.4473    1.2464    4.0444    1.2413    2.6900   16.6996    3.0000
     12.9187   60.9303    1.5128    3.4454    1.2593    2.2976   15.4214    3.0000
      4.8807   11.4097    1.4971    2.0412    1.2105    1.7832    5.7704    2.0000
      5.7536   22.7122    1.1432    1.8351    1.2305    2.1097    9.1543    3.0000
another example:
s =
     -3.8660    3.8000    1.8212    1.0659    0.9359    1.1195   -4.2488    4.0000
      5.6911    1.6000    1.8920    1.0000    1.0772    1.1631    7.5085    6.0000
      1.6582   31.9250    1.1889    1.0221    1.1091    1.1899    2.0074    5.0000
     -3.0589    1.1000    1.6842    1.0184    0.9804    1.1165   -4.5364    4.0000
Such that I will have an alert that I only have one observation of , say 1.00 in the first piece of data, but 5 and 6 in the second piece?
Thanks, Kate

Best Answer

How about
 counts = accumarray( s(:,end), 1 ) ;
In the first case, it gives
 counts =
     1
     3
     6
In the second case
 counts =
     0
     0
     0
     2
     1
     1
As you can see, the i-th element of vector counts is the count of data i. And then you can process counts as you want/need, e.g.
 is1 = counts == 1 ;
 if any( is1 )
     fprintf( 'Warning, the following data blabla..\n' ) ;
     disp( find( is1 )) ;
 end
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