Andrews curves for visualization of multidimensional data.
step determines the number of line segments for each curve.
If ymax==NA then the maximum y coordinate will be determined from the curves.
Note that for type==3 the x range is \([0, 4*pi]\) otherwise \([-pi, pi]\).
Andrews, D. F. (1972) Plots of High-Dimensional Data. Biometrics, vol. 28, no. 1, pp. 125-136.
Khattree, R., Naik, D. N. (2002) Andrews Plots for Multivariate Data: Some New Suggestions and Applications. Journal of Statistical Planning and Inference, vol. 100, no. 2, pp. 411-425.