Presentation of the MW-pI plot for Phase I data sets. Each sequence entry's corresponding protein is represented by a (MW, pI) tuple, therefore, the entire collection can be plotted onto a two-dimensional space. To highlight the difference of population densities among different regions of the graph, a variable called density is employed. It controls the color of the scattered points on the plot, where the plot space is viewed as a grid that consists of many small cells each of which has a length of 10 KDa along the X-axis and a width of 0.1 pH along the Y-axis. Each cell's local population (the number of points that fall into that region) is recorded and its ratio over the entire population is calculated. Since most of the ratios are very small numbers, they have been multiplied by 10000 before they are used in plotting the graph.