Extrapolation to lower radii

Next we investigated the relationship between planet size and occurrence rate by creating an entirely new plot to make comparisons not included in Petigura et al. (2013). This plot was created in very much the same fashion as Figure 5 (see above), except that the x-axis has been changed to planetary radius. As in Figure 5, cumulative occurrence is plotted, this time as fraction of stars possessing planets with radii larger than \({R_\oplus}\). Only planets with flux values greater than 10 and less than 400 \({F_\oplus}\) have been included to reduce error caused by undersampling of planets outside of this range. A similar extrapolation using a log regression was performed to infer the occurrence rate of planets with very small radii (ie. less than 1 \({R_\oplus}\)). Additionally, each blue X represents an individual occurrence rate (as calculated by Group 1) for each planet in the set. These two plots confirm that occurrence rate is relatively flat for planets with radii between 1 and 3 Earth radii.