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Is there a function that produces an ISODATA unsupervised classification in QGIS?

The only unsupervised classification function I can find is a KMeans.

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  • The ISODATA classifier is really just a modified form of the K-means classifier, with the ability to split classes with too much variance and merge classes that are too similar between each iteration. Although widely used, one problem with this approach is that it can be difficult to converge. Mather and Koch (2011) suggest an alternative in which the process starts with an overestimate of the number of classes and then simply merges (i.e. there is no splitting of classes). The open-source GIS Whitebox Geospatial Analysis Tools has this classifier but not ISODATA if that helps. Commented Sep 3, 2014 at 12:51
  • @WhiteboxDev, do you have links for the reference and for the software?
    – Johanna
    Commented Sep 3, 2014 at 22:13
  • The reference is Mather and Koch (2011) Computer Processing of Remotely-Sensed Images 4th ed. page 239 "A modified k-means algorithm". I've implemented this algorithm in Whitebox GAT, available here: uoguelph.ca/~hydrogeo/Whitebox I'm sure that there are other open-source software implement similar unsupervised classification algorithms too. Commented Sep 4, 2014 at 11:02
  • Thank you for those links. They are helpful for me in the long run - if not immediately.
    – Johanna
    Commented Sep 9, 2014 at 1:01

1 Answer 1

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An old post, but just as an update;

In QGIS >= 2.18.14, there is a ISODATA Clustering for Grids tool, under SAGA | Image analysis.

Some additional detail about the module is found here: Module ISODATA Clustering for Grids.

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  • There's a conflict with the Statistics parameter for this tool. In QGIS 2.18 it is a required input, whereas in the official documentation it is an output. I've tried to specify the statistics file generated for a given raster by QGIS (*.tif.aux.xml), but it is an unsupported file type.
    – 15Step
    Commented Apr 30, 2018 at 13:34
  • @15Step it's quite true, confirmed in QGIS 2.18.19.
    – Kazuhito
    Commented Apr 30, 2018 at 15:25
  • @15Step This problem persists today with QGIS 3.4.11
    – Kartograaf
    Commented Oct 9, 2019 at 19:29

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