  Several methods have been proposed to estimate the number of clusters in a
dataset; the basic ideal behind all of them has been to study an index that
measures inter-cluster separation and intra-cluster cohesion over a range of
cluster numbers and report the number which gives an optimum value of the
index. In this paper we propose a simple, parameter free approach that is like
human cognition to form clusters, where closely lying points are easily
identified to form a cluster and total number of clusters are revealed. To
identify closely lying points, affinity of two points is defined as a function
of distance and a threshold affinity is identified, above which two points in a
dataset are likely to be in the same cluster. Well separated clusters are
identified even in the presence of outliers, whereas for not so well separated
dataset, final number of clusters are estimated and the detected clusters are
merged to produce the final clusters. Experiments performed with several large
dimensional synthetic and real datasets show good results with robustness to
noise and density variation within dataset.
