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I'm using graduated style of a point layer to assign a colour ramp to symbols (squares). I assigned manual values to class intervals specifying classes to be:

0.60 - 0.80
0.80 - 1.00

That is, in entering class bounds for a lower class I used 0.600000 as lower value and 0.800000 as upper. And then 0.800000 as lower for next class.

How are then the class intervals constructed in such case? Are they:

(0.60 - 0.80)
[0.80 - 1.00)

Or:

(0.60 - 0.80]
(0.80 - 1.00]
...
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The second option you gave corresponds to how QGIS deals with intervals:

(0.60 - 0.80]
(0.80 - 1.00]

If a point value is 0.8 it will be rendered with the symbol you assigned to the first class, 0.60 - 0.80.

I think this should be reflected in the legend accordingly. That is, one should come up with something to indicate users that even if the same value is in two different classes (in a class it's the max value and in the next class it's the min value), a point value would lie in only one of them. For instance:

enter image description here

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    Thank you gcarrillo. Indeed - I also believe that should be made clear in the legend how the intervals close. Have you ever seen that documented anywhere? I couldn't came across any authoritative link. – radek Feb 3 '15 at 9:09
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    Not really, I realized it by pure observation. If you read the docs, there is no reference to the extreme values of each class. (BTW, didn't I answer your question already?) – Germán Carrillo Feb 3 '15 at 12:25
  • Thanks for this, I used graduated symbology before and always avoided using the same values for both upper and lower limits. Atleast now it makes sense :) – Joseph Feb 3 '15 at 14:22
  • Yes, it's not clear what will happen with those extreme values, and sometimes it's also a bit unclear to create classes like these: 0.1-0.2, 0.21-0.3, because it implies that there is a gap from 0.2 to 0.21. – Germán Carrillo Feb 3 '15 at 14:28
  • @gcarrillo, good point. I will note this the next time I use Graduated symbology as it can significantly alter the visualisation. – Joseph Feb 3 '15 at 14:42

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