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2.6 Population filtering

Filtering of datasets is done by using the drop or keep commands after you have first created a dataset using an import command:

 
import ds/BEFOLKNING_KJOENN as gender
drop if gender == '1'

In microdata.no, if-expressions may be used in many contexts. The following common logical operators are possible to use:

  • Larger than: >

  • Less than: <

  • Equal to: ==

  • Larger than or equal: >=

  • Less than or equal: <=

  • Not equal: !=

  • Or: |

  • And: &

The following expression will remove individuals under 18 years from your population:

 keep if age >= 18

Values for missing data can be assigned as follows:

 sysmiss(<variable>)

Individuals with no data on wage income can be removed from your population as follows:

 drop if sysmiss(wage)

It is also possible to create random samples from a dataset. The command sample may be used for such purposes. For more about syntax and examples, use the command help sample.