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kdbq-lang

Adding Columns in kdb based on other columns value

I have a column like this in dataframe named test:

Name    Client
 A       P
 B       Q
 C       R
 D       S
 E       T

I need to to create a new column clienttype in the same dataframe with condition that, if Client = P or Q clienttype = first. If client type = R or S clienttype = second and so on. Can anyone tell how to do this in kdb? Thanks

Solution

  • Could this be solved with a dictionary?

    q)update ClientType:(`P`Q`R`S!`first`first`second`second)Client from tab
Name Client ClientType
----------------------
A    P      first
B    Q      first
C    R      second
D    S      second
E    T

    Extension to this: You can also use vector conditionals ?[;;] for these types of problems. Unfortunately in this case in would result in many nested vector conditionals:

    update Clienttype:?[Client in`P`Q;`first;?[Client in`R`S;`second;`third]]from tab
Name Client Clienttype
----------------------
A    P      first
B    Q      first
C    R      second
D    S      second
E    T      third

    If you only had two possible options (e.g. first and second) this approach could prove useful.