One simple examle to estimate the NDVI and DVI from the R, G, NIR, SWIR data.
>>> from vilib.vilib import vi
>>> g = np.random.randn(100)
>>> r = np.random.randn(100)
>>> nir = np.random.randn(100)
>>> swir = np.random.randn(100)
>>> foo = vi(g,r,nir,swir)
>>> ndvi = foo.get_vi('ndvi') # calculate the NDVI
>>> dvi = foo.get_vi('dvi') # calculate the DVI