To use the « Flows » representation, it is necessary to lean on a data matrix.
In some cases, this matrix presents exchanges between different geographic levels, for instance between municipalities and provinces.
In the matrix beneath, we can observe exchanges between municipalities on the one hand (identified by the INSEE code), and an exchange between a municipality and a province on the other hand (in the last line, from Dignes les Bains until les Bouches du Rhône).
|Identifiants(départ > arrivée)||Valeurs|
In order to insert this matrix in Cartes & Données, it would be necessary to have a base map mixing up the two kinds of identifiers: municipality codes and provinces codes. If such base maps do not exist by default, yet they can be conceived very simply in Cartes & Données with the help of the « Union » operator module.
To do so, just link the municipal base map and the provincial base map to the « Union » module which will then constitute a new base map gathering all the geographical entities.
As this « Union » module is a base map, it is then possible to attach to it a « Data » module in order to insert our matrix.