How to convert strings in a table to numbers?

I have a very large table (611507 x 7) where some columns are strings and need to be converted to numbers.
On the other hand, there are repeated strings in the same columns, which should have the same process when they are converted into numbers.How should I do this?
Part of the table data

'longitude' 'user id'
121.470259000000 'edbc54bddf16494a49f39ac057b4185d'
121.470259000000 'f8206ab58b9bdb070673f7050242e9ee'
121.470259000000 'f8206ab58b9bdb070673f7050242e9ee'
In fact, the column related to
'user id'
should be converted to a number, and for example, rows 2 and 3, which are duplicates, should be converted in this way:
1
2
2

Answer 1

[Karim]

An easy method would be to use the third output of the unique command. This will work directly on strings and will give the coressponding index as a number.

% create the table...
Longitude = [121.470259; 121.470259; 121.470259];
UserID = ["edbc54bddf16494a49f39ac057b4185d";"f8206ab58b9bdb070673f7050242e9ee";"f8206ab58b9bdb070673f7050242e9ee"];
MyTable = table(Longitude,UserID)

MyTable = 3×2 table
    Longitude                  UserID              
    _________    __________________________________

     121.47      "edbc54bddf16494a49f39ac057b4185d"
     121.47      "f8206ab58b9bdb070673f7050242e9ee"
     121.47      "f8206ab58b9bdb070673f7050242e9ee"

% extract the UserID and convert it into an index...
[~,~,MyTable.UserID_Idx] = unique(MyTable.UserID)

MyTable = 3×3 table
    Longitude                  UserID                  UserID_Idx
    _________    __________________________________    __________

     121.47      "edbc54bddf16494a49f39ac057b4185d"        1     
     121.47      "f8206ab58b9bdb070673f7050242e9ee"        2     
     121.47      "f8206ab58b9bdb070673f7050242e9ee"        2     

[Tara]

Thank you very much for your help