[i] Pearson coefficient is calculated as [TeX:] \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(-1{\leq}r={\Sigma}(x_{i}-{\bar{x}})(y_{i}-{\bar{y}}{/}\sqrt{{\Sigma}(x_{i}-{\bar{x}})^{2}{\Sigma}(y_{i}-{\bar{y}})^{2}}{\leq}1\) \end{document} , where x and y are the logarithms of expression levels of the two genes, i indexes the cell, and the bar indicates average. r close to 1 signifies strong positive correlation, while a value close to zero means no correlation. Negative r value would be anti-correlation.