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I have to provide choropleth maps for for Energy savings, Emission savings, Cost Savings related to different administrative boundaries such as provinces and states, but I don't know which classification is more appropriate because my data for each province is separated from other parts and there is no link between the numbers. Any suggestion for how should I classify? I don't want to use equal intervals because the minimum is 20 and the maximum is 400 and there are few over 300 figures so equal intervals represent my data not in a good way, but about other methods such as jenks or deviation or quantile I have no idea!

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    Quantile is good, but you would have to make sense of "my data for each province is separated from other parts and there is no link between the numbers." For example, if Province A has values between 0.1 and 0.9 which are unrelated to Province B's values of 10-99, the quantile map -- with percentiles determined across all the provinces -- will be meaningless. Much better to get them on a common scale, even if you have to create some sort of index to do so. – J Kelly Dec 26 '16 at 23:59
  • My intention is to show which province has the minimum and which one has the maximum energy savings and then show that the rest are, with varying degrees, in between, also, I have only 20 data, and from what I know, Quantile put the same number of data in each class. So, I decided not to use quantile and instead I used Jenks because It looked better when I tried all the methods. Am I wrong about quantiles? and also, how about pretty breaks? – Arbo94 Dec 27 '16 at 16:40
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    Yes, you're right about quantile. It's a way to make it look like "something is going on" if your data is fairly dull. In Arc, and I assume in QGIS as below, you can actually slide those break lines around to get any division of classes you like, whatever looks pretty to you! – J Kelly Dec 27 '16 at 17:07
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I've been experiencing the same kind of problem. The solution that I worked out at the time was using the 'Histogram' option in Qgis. In this option you can manually determine the classification of your graduated map. You can slide the vertical line to the appropriate value.

HIstogram

It's actually a very handy tool to use, since you can also see how many features will be captured in one class. This way you will be able to represent your data in the most desired way. (I Hope!)

  • Thank you! This was very helpful actually. But one question, I have 20 data and when I load them in the histogram only 10 is shown. Is there something wrong, or it is always like this? – Arbo94 Dec 27 '16 at 16:39
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    Do you mean that you got 20 different features? Not entirely sure what you mean with 20 data. The data might not be visual or the classification might not include them. – Douwe Vermeer Dec 28 '16 at 7:22
  • I just have 20 final result's number for the amount of energy saved in each province in 2030 for example. – Arbo94 Dec 28 '16 at 12:55
  • I can't edit my previous comment... by number I mean value. for example, I've calculated that the maximum energy saving would be 400 GWh and the minimum would be 1.5 GWh among these 20 provinces. – Arbo94 Dec 28 '16 at 12:59

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