Method and program for drawing distribution area of data points on coordinate plane

A non-transitory computer-readable recording medium having recorded thereon a program for drawing the distribution area of the data points on the coordinate plane, the program causing a computer to perform a method for drawing a distribution area of data points on a coordinate plane, the method comprising:

• a first step of selecting representative points in which any one data point of a data group containing plural data having a pair of variables is selected as a first representative point on the coordinate plane where the data of the data group are expressed as points;
• a second step of selecting the representative points in which
• assuming that one of a clockwise direction and a counterclockwise direction is set as a rotation direction for making selection, the first representative point is set as a first standard point, and any direction passing through the first standard point is set as a first direction for selecting a corresponding one of the representative points,
• the data point corresponding to a direction in which a minimum angle is formed with respect to the first direction for selecting the corresponding one of the representative points in the rotation direction for making selection as viewed from the first direction for selecting the corresponding one of the representative points, among plural first directions of the data points toward the respective data points via the first standard point is selected as a second representative point;
• a third step of selecting the representative points in which
• assuming that the second representative point or an immediately preceding representative point which is a representative point selected in the third step and a most recently selected representative point is set as a next standard point, the standard point used for selecting the immediately preceding representative point is set as an immediately preceding standard point, and any direction within 180 degrees in the rotation direction for making selection from a direction toward the immediately preceding standard point via the next standard point is set as a next direction for selecting the corresponding one of the representative points,
• the data point corresponding to a direction in which a minimum angle is formed with respect to the next direction for selecting the corresponding one of the representative points in the rotation direction for making selection as viewed from the next direction for selecting the corresponding one of the representative points, among plural next directions of the data points toward the respective data points other than the immediately preceding representative point via the next standard point is selected as a next representative point, the third step repeatedly performing processing of selecting the next representative point;
• and
• a step of drawing the distribution area in which the representative points are connected by a line to draw a distribution area indication line.