Using the field calculator to replace the character in QGIS

Question

How to use the field calculator to replace the character - in part of the values with the character "B" at the end of this value? I also want to replace the other values without symbol - replace with the symbol "F" at the end of these values. Like this -0345 to 0345B, 0341 to 0341F.

field calculator qgis regular expression replace

Zoltan · Accepted Answer

You can use regexp_replace function in field calculator:

The expression
regexp_replace(  "linecode", '^-(.*)$', '1B')

will replace '-' + 'any string'  with  'any string' + 'B'. So it will change string '-0345' to '0345B'. 1 refer to the expression part in brackets. You may give more specific regexp instead of '.*'.

The second expression will add 'F' to numeric strings:
regexp_replace( "linecode", '^([0.9][0-9]*)$', '1F')

It will replace only string made of numeric characters [0.9], so you can use it after the previous expression without selection in the table.

Kadir Şahbaz · Answer

Use this expression: if(left(linecode, 1) = '-', substr(linecode, 2) + 'B', linecode + 'F')
I suggest to create new field instead of changing the existing one. You may need the original one later.

Using the field calculator to replace the character in QGIS

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