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I have a shapefile of a lot of polygons. I calculated perimeter of each polygon and some polygons returned nan values as they have hole/ring. I am looking for a way to select the polygons with 'nan' value in QGIS. "column_name" = 'nan' seems to be an invalid expression in QGIS.

How do I select them?

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    Select the ones greater than 0 and invert selection? NaN is not a number so shouldn't be greater than 0 (or less than or equal to).
    – Michael Stimson
    Commented Apr 4, 2019 at 5:50
  • This worked, thank you so much!
    – Sher
    Commented Apr 4, 2019 at 5:55
  • 4
    having a hole should not break the perimeter calculation, more likely those polygons are invalid
    – Ian Turton
    Commented Apr 4, 2019 at 7:25
  • Thanks Ian, you are right. Actually these polygons have been converted from raster image. I simplified the polygons, so there is no nan values anymore.
    – Sher
    Commented Apr 4, 2019 at 7:33
  • better than simplifie, may be the processing called "Fix"
    – Christophe P.
    Commented Apr 4, 2019 at 9:51

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