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I'm pretty new to GIS in general and I'm trying to take an absolute value of the difference between two fields in field calculator when creating a new field, but using ABS () returns an invalid expression in Preview. ABS () is not listed on the supported expressions--is there a way around this? Thanks! John

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You seem to use QGIS 1.8, because the development version (soon to be 2.0) supports abs().

Instead, you can use


... replace value with your attribute.

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