def dev_ij(i,j,traj_exp,adj_mat): 
t=np.asmatrix(traj_exp) <EOL>wh=np.where(adj_mat[i]><NUM_LIT:0>) <EOL>return np.sum(np.square(t[i,j]-t[wh,j],dtype=float),dtype=float)<EOL>
Function returns the sum of squared differences in the expression of a gene, per cell
:param i: int representing the index of the cell being processed 
:param j: int representing the index of the gene being processed
:param traj_exp: ndarray representing gene expression
:param adj_mat: ndarray representing the calculated adjacency matrix
:return: float representing the sum of squared differences