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How do I go about to perform a band ratio and Principal Component analysis in QGIS? I need to derive principal components from ratios of landsat TM bands .

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If you have GRASS GIS, it's easy i.pca –  Chethan S. Apr 17 '13 at 8:52
Thanks I will give it a go –  Kemp Apr 17 '13 at 8:54
I would like to reply in detail on this. However, I don't understand the point behind deriving Principal Components from ratios. Elaborating on a simple example, you mean like: calculate Ratio 1 = Band 4 / Band 3, calculate Ratio 2 = Band 4 / (Band 4 + Band 3), then derive PCs from Ratio 1 & Ratio 2? –  Nikos Alexandris Oct 12 '13 at 8:41

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