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How to select nan values in QGIS

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1

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?

qgis polygon select

share|improve this question

edited Apr 4 at 6:35

Erik

3,429322

asked Apr 4 at 5:32

SherSher

18111

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  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
  Apr 4 at 5:50
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  This worked, thank you so much!
  
  – Sher
  Apr 4 at 5:55
  

  
  
  
  


• 
  
  
  

  
  4
  

  
  
  
  
  
  

  
  
  having a hole should not break the perimeter calculation, more likely those polygons are invalid
  
  – Ian Turton♦
  Apr 4 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
  Apr 4 at 7:33
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  better than simplifie, may be the processing called "Fix"
  
  – Christophe
  Apr 4 at 9:51
  

  
  
  
  

 | 
show 1 more comment

1

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?

qgis polygon select

share|improve this question

edited Apr 4 at 6:35

Erik

3,429322

asked Apr 4 at 5:32

SherSher

18111

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  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
  Apr 4 at 5:50
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  This worked, thank you so much!
  
  – Sher
  Apr 4 at 5:55
  

  
  
  
  


• 
  
  
  

  
  4
  

  
  
  
  
  
  

  
  
  having a hole should not break the perimeter calculation, more likely those polygons are invalid
  
  – Ian Turton♦
  Apr 4 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
  Apr 4 at 7:33
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  better than simplifie, may be the processing called "Fix"
  
  – Christophe
  Apr 4 at 9:51
  

  
  
  
  

 | 
show 1 more comment

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?

qgis polygon select

share|improve this question

edited Apr 4 at 6:35

Erik

3,429322

asked Apr 4 at 5:32

SherSher

18111

share|improve this question

edited Apr 4 at 6:35

Erik

3,429322

asked Apr 4 at 5:32

SherSher

18111

share|improve this question

edited Apr 4 at 6:35

Erik

3,429322

asked Apr 4 at 5:32

SherSher

18111

edited Apr 4 at 6:35

Erik

3,429322

edited Apr 4 at 6:35

Erik

3,429322

asked Apr 4 at 5:32

SherSher

18111

asked Apr 4 at 5:32

SherSher

18111