how to use Discretize syntax

Hello all,

I have a data set, in that one column got 1 -29 range of numbers i want to group them same nembers like

1 -4 = claas1

5-9 = class2 so on class7

how can i do this with discretize syntax ?

[Bhaskar R]

This may help, refer this

https://in.mathworks.com/help/matlab/ref/double.discretize.html

Answer 1

[John D'Errico]

Funny. Actually, both of the other answers have missed an important point. While they properly describe how to use discretize, both Star and Adam got the class boundaries wrong. :) What they did not notice was the classes described as 1:4, 5:9, etc are not equal in width. So using colon to create classes as they did will create the wrong class bounds.

Assume you want 1-4 in class 1, 5-9 in class 2, 10-14 in class 3, 15-19 in class 4, etc. You only told us what the first two classes were, so I cannot be sure. But both Adam and Star said to use bin edges of 1:4:29.

1:4:29
ans =
     1     5     9    13    17    21    25    29

The bins should be a list of the LOWER bounds for each class.

So 1:4:29 as the bin edges will put 5 and 9 in DIFFERENT classes.

Instead, the correct set of bin edges would have been something like 1 5 10 ...

I'll suggest that instead, the bin edges might properly have been 0:5:30.

g = discretize(data, 0:5:30);

That makes the first bin go down to 0, but who cares? Since you never have a point at 0, that it starts at 0 is irrelevant. Otherwise, if your boundaries are unequal in width all the way, you might do something like this:

g = discretize(data, [1 4 10 17 20 23 30]);

[Adam Danz]

I was assuming the example given in the question was wrong since the indexing 1:4:29 worked out nicely but maybe I shouldn't have assumed that!

[Star Strider]

We do not currently know how Archana Katageri wants to define the bins, since a complete description was not provided.

[John D'Errico]

Yes, but my point was that 1:4:29 does not work. It puts 5 and 9 in different bins.

[4:9;discretize(4:9,1:4:29)]
ans =
     4     5     6     7     8     9
     1     2     2     2     2     3

And the request was 5:9 should be in bin 2. I think the problem was the bin bounds indicated by the question were non-uniform in width, even for only 2 bins. Odds are that was just a mistake by the OP. But, you never know...

Answer 2

[Adam Danz]

data = randi(29,100,1);         % demo data (100 values between 1:29
g = discretize(data, 1:4:29)    % g is the group number, groups defined by 1:4:29

% Check results
T = table(data, g, 'VariableNames',{'Data','Group'})

Answer 3

[Star Strider]

Try this:

Data = [randi(29, 20, 1) rand(20, 5)];                      % Create Data, ID Numbers 1-29 In First Column
ClassVct = 1:4:29;                                          % Define Bins
ClassMtx = discretize(Data(:,1), ClassVct);                 % Discretize Data By Bins

Experiment to get the result you want.

EDIT — (01 Nov 2019 at 13:27)

To separate the identified rows in ‘Data’ into cell arrays for each group identified in ‘ClassVct’:

Groups = accumarray(ClassMtx, (1:numel(ClassMtx))', [], @(x){Data(x,:)});

To test that, check with:

Groups{1}
Groups{end}

or similar.