From Raster—Spectral—Principal Component.
Look at the output text in a text editor. Arrange it similar to this and calculate the variance (2nd row value / sum of 2nd row). If you wish you can rerun PCA on your original file and only use the first 2 or 3 components (in this example). You could use only 2 but since there are three display bands I would use the first 3.
January 16, 2017 @ 3:53 am
hi
i am mustafa from iraq
i study rs can you help me ?