[posMatrix,retVals]=ShNeigh(heatmapMatrix,method_type)
Input: heatmapMatrix: heatmap matrix method_type: 1 for ShNeigh1; 2 for ShNeigh2
Output: posMatrix: N*4 matrix, the first column is a vector that marks valid genome loci, columns 2-4 are coordinates retVal: a structure that contains some additional information