[GIS] Changing class break schemes in QGIS to eliminate overlap

qgissymbology

When using Graduated Symbology in QGIS, by default the bounds seem to be overlapping. For example, class 1 shows 0-100.000; class 2 shows 100.000-200.000; class 3 shows 200.000-300.000 where it appears as though the value 100 is captured in class 1 & 2; 200 is captured in class 2 & 3.

Is there a way to change the default class breaks so they are not overlapping (e.g. Class 1 = 0-100; class 2 = 101-200; class 3 = 201-300)?

I know in ArcGIS you can adjust the number of decimal points in the label.

Best Answer

Uncheck "Link class boundaries" under "Layer Properties" >> "Style"

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[GIS] Changing graduated color class values with ArcPy

I just had this exact same issue running ArcGIS 10.2. It turns out that (in 10.2 at least) you cannot set the symbology values via classBreakValues when the valueField is in a joined table. Instead, you need to export everything to a new feature class first, and then the following code should work:

if lyr.symbologyType == "GRADUATED_COLORS":
    lyr.symbology.valueField = "NewField_Variance" #Placeholder name
    lyr.symbology.classBreakValues = [-.01, .01, .0866]
    lyr.symbology.classBreakLabels = ["-8.66% to -1.00%", "-.99% to 1.00%","1.01% to 8.66%"]

I'm about to upgrade to 10.3--hopefully it will be fixed.

Hat tip to this post on the Esri forums by simontp, which in turn references this post by cheffing.

[GIS] How to eliminate polygon overlap areas in QGIS

You can use Eliminate sliver polygons tool to eliminate the small polygons, as you can see below:

You have two options to eliminate polygons:

Area: eliminate polygons based on area in which the smaller polygon will be eliminated if they area located inside big polygons
Common boundary: if there is a common boundary between two polygons, they will be eliminated.

In your case, since you need the smaller polygons to be eliminated, I think option 1 is the best one for you.

You can find Eliminate sliver polygons tool from Vector -> Geoprocessing tools -> Eliminate sliver polygons

Best Answer

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[GIS] Changing graduated color class values with ArcPy

[GIS] How to eliminate polygon overlap areas in QGIS

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