I would like to graduate from a column of mine with decimal numbers. For this I want to apply the Jenks discretisation and exclude zero. I tried this, but it didn’t work…

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Do you have any idea to do that?

  • try enclosing the column name in "" – ThingumaBob Sep 21 at 9:46
  • I tried : "I_EVEPOP" > 0 and "I_EVEPOP" > '0' but doesn't work... – VioGeo Sep 21 at 9:58
up vote 5 down vote accepted

Your query of:

I_EVEPOP > 0

Is a binary question. You are asking QGIS, is it bigger than 0. If so it will show a 1, if not it will show a 0.

What you want is a conditional:

CASE WHEN I_EVEPOP > 0 THEN I_EVEPOP END

"I_EVEPOP" > '0' should work.

Columns, when referenced in equations, need to be put in double quotation marks, any value you want to place, grab or check for in single marks.

  • I tried but still don't work... – VioGeo Sep 21 at 9:56

You need to switch to Rule-based styling to remove 0 value from the classification. You can use Graduated classification first to classify your data using the desired column as it is and using Mode: Natural Breaks (Jenks) as you can see below:

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However, to remove the 0 value you need to switch to Rule-Based classification, and as you can see in the following image, the highlighted rule shows the ColumnName >= Value. In this example New_ID >= 0.000

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You need to change it to New_ID > 0.000 by removing the equal = sign. But in this case the polygon with the value equal zero will disappear.

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  • Actually, I would like the discretisation to be calculated without the 0. If I do that the discretisation integrated the 0 values. – VioGeo Sep 21 at 11:21

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