QGIS Regex substring for Labelling

Question

I'm trying to plot a series of contours in QGIS based on dxf data exported from some specialised mining software. The attirbute output is pretty ugly and merges a few fields together.

DXFName=C5ドル DXFGroup= DXFFeature= DXFValue=50.0 DXFDescription=Major contour at level 50.000 DXFPrimitive= DXFLine=0 DXFPattern=0

I need to extract just the 'DXFValue=' value to allow categorised symbology, and labelling of the contours.

I've played around with rule based symbology using the 'regexp_substr' function, but I don't have the regex knowledge to produce what I need.

Anyone able to assist?
Thanks!

Answer 1

You can use the following expression to extract the values you want:

regexp_replace("test", '.*DXFValue=([0-9\.\-]{1,}).*', '\1円')

This function replaces the entire string with the first matched group (the '\1円'), which is the string contained in the brackets '([0-9\.\-]{1,})', coming after 'DXFValue='.

Remember to set the output field type to 'Decimal number (real)'.

field calculator

• Nathan W: regexp_substr has just been fixed to return the first match group, regexp_substr('yourstring', 'DXFValue=(\\d*.\\d*)') should now work. github.com/qgis/Quantum-GIS/commit/…