7.4 In a printing system CMYK values are sampled between 0 and 255 in a uniform grid to obtain up to 104 input–output characterization data. Patches are printed and measured by the spectrophotometer. The spectra are measured at 31 wavelengths from 400 to 700 nm at 10 nm intervals. Use PCA mathematical techniques to analyze the set of multivariate input–output characterization data. Show the DE (DEab * , DE2000) error plot with respect to number of principal components. Determine the parameter matrix using least squares. Plot the model accuracy for the test colors as a function of the number of basis vectors. How many basis vectors are needed to obtain a reasonably accurate model?