Nearest neighbor vector analysis of sdss dr5 galaxy distribution
  We present the Nearest Neighbor Distance (NND) analysis of SDSS DR5 galaxies. We give NND results for observed, mock and random sample, and discuss the differences. We find that the observed sample gives us a significantly stronger aggregation characteristic than the random samples. Moreover, we investigate the direction of NND and find that the direction has close relation with the size of the NND for the observed sample. 
Yongfeng Wu, Weike Xiao, Rongjun Mu, David Batuski, Andre Khalil
astro-ph.CO