1. A partitioning method of partitioning a set of objects (X), comprising: a first iterative partitioning step (S0 to S3) which utilizes a first partition (P 0 ) formed by classes that contain an object and which at each iteration (i) combines two classes that maximize a criterion of similarity for creating a new partition (Pi&plus; 1 ) used as an initial partition for the next step, until a partition (P N−1 ) is obtained that contains only a single class, a selection step (S4) of selecting from the obtained partitions, a partition (PY 0 ) which comprises an optimal number of classes (M), characterized in that it comprises: a step (S6) of calculating elements (Y 0, j ) which are representative of classes of the selected partition, a second iterative partitioning step (S7, S8) which utilizes the selected partition as a first current partition (PY i ) and which, at each iteration (i), creates a new partition (PY i&plus;1 ) by associating each object of said set (X) with the element which represents the current partition (Y i, j ) it is closest to, and calculates elements (Y i&plus;1, j ) which are representative of classes of the new partition (PY i&plus;1 ), the new partition forming the current partition for the next iteration, until the elements which are representative of the new partition are identical with the elements which are representative of the current partition (Y i&plus;1, j &equals;Y i, j ).