Filling a field with automatic numbering specific by unique value of another field with QGIS expression

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I have a table with 2 fields: NUMBER (integer) and TOWN (text).
I would like to find an expression that fills the NUMBER field with an automatic number specific for each value of TOWN.
Example:
NUMBER | TOWN

----------------------

1 | STRASBOURG

2 | STRASBOURG

3 | STRASBOURG

1 | PARIS

2 | PARIS

1 | TOULOUSE

2 | TOULOUSE

3 | TOULOUSE

4 | TOULOUSE

How can I do that with a QGIS expression ?






qgis expression







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    up vote
    1
    down vote

    favorite












    I have a table with 2 fields: NUMBER (integer) and TOWN (text).
    I would like to find an expression that fills the NUMBER field with an automatic number specific for each value of TOWN.
    Example:
    NUMBER | TOWN

    ----------------------

    1 | STRASBOURG

    2 | STRASBOURG

    3 | STRASBOURG

    1 | PARIS

    2 | PARIS

    1 | TOULOUSE

    2 | TOULOUSE

    3 | TOULOUSE

    4 | TOULOUSE

    How can I do that with a QGIS expression ?






    qgis expression







    share|improve this question























      up vote
      1
      down vote

      favorite









      up vote
      1
      down vote

      favorite











      I have a table with 2 fields: NUMBER (integer) and TOWN (text).
      I would like to find an expression that fills the NUMBER field with an automatic number specific for each value of TOWN.
      Example:
      NUMBER | TOWN

      ----------------------

      1 | STRASBOURG

      2 | STRASBOURG

      3 | STRASBOURG

      1 | PARIS

      2 | PARIS

      1 | TOULOUSE

      2 | TOULOUSE

      3 | TOULOUSE

      4 | TOULOUSE

      How can I do that with a QGIS expression ?






      qgis expression







      share|improve this question













      I have a table with 2 fields: NUMBER (integer) and TOWN (text).
      I would like to find an expression that fills the NUMBER field with an automatic number specific for each value of TOWN.
      Example:
      NUMBER | TOWN

      ----------------------

      1 | STRASBOURG

      2 | STRASBOURG

      3 | STRASBOURG

      1 | PARIS

      2 | PARIS

      1 | TOULOUSE

      2 | TOULOUSE

      3 | TOULOUSE

      4 | TOULOUSE

      How can I do that with a QGIS expression ?






      qgis expression




      qgis expression






      share|improve this question













      share|improve this question











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      asked 1 hour ago









      Etienne

      854




      854




















          1 Answer
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          Finally, I found the right expression to do that:



          "TOWN" ||( @row_number - minimum( @row_number , "TOWN") +1)





          share|improve this answer






















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            1 Answer
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            active

            oldest

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            1 Answer
            1






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes








            up vote
            3
            down vote













            Finally, I found the right expression to do that:



            "TOWN" ||( @row_number - minimum( @row_number , "TOWN") +1)





            share|improve this answer


























              up vote
              3
              down vote













              Finally, I found the right expression to do that:



              "TOWN" ||( @row_number - minimum( @row_number , "TOWN") +1)





              share|improve this answer
























                up vote
                3
                down vote










                up vote
                3
                down vote









                Finally, I found the right expression to do that:



                "TOWN" ||( @row_number - minimum( @row_number , "TOWN") +1)





                share|improve this answer














                Finally, I found the right expression to do that:



                "TOWN" ||( @row_number - minimum( @row_number , "TOWN") +1)






                share|improve this answer














                share|improve this answer



                share|improve this answer








                edited 10 mins ago









                ahmadhanb

                19.5k21846




                19.5k21846










                answered 24 mins ago









                Etienne

                854




                854



























                     

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