clear all clc t=0:1/1000:10-1/1000 s=sin(2*pi*t) snr=20 s_power=var(s) varience of s linear_snr=10^(snr/10) factor=sqrt(s_power/linear_snr) noise=randn(1,length(s))*factor x=s+noise Ó É SNR¼ Æ Ë ã 

The random walker algorithm was introduced in the paper: Leo Grady and Gareth Funka-Lea, "Multi-Label Image Segmentation for Medical Applications Based on Graph-Theoretic Electrical Potentials", in Proceedings of the 8th ECCV04, Workshop on Compute

Econometric Reviews, Vol. 31, No. 3, pp. 245-296, 2012.