An example of StepMiner2D. (a) Scatter plot of ESR1’s gene expression and methylation. The dotted lines indicate threshold identified by StepMiner2D. (b) Scatter plot of rank transformed data. (c) Heatmap showing a non-decreasing surface sitting on top of the rank transformed data. (d) Three-dimensional visualization of points on the non-decreasing surface and the best fit bivariate step function.