20.2.7  Power regression

The power_regression command finds the graph y=bx^m which best fits a set of data points.

• power_regression takes two arguments:
  • xcoords, a list of x-coordinates.
  • ycoords, a list of y-coordinates.
  You can combine two arguments into a matrix with two columns (each list becomes a column of the matrix).
• power_regression(xcoords,ycoords) returns a sequence m,b of the numbers in the best fit power equation y=b x^m.

Example

or:

so the best fit (in this case, exact fit) power curve will be y=1.0 x².

The power_regression_plot command draws the best fit power function.

• power_regression_plot takes two arguments:
  • xcoords, a list of x-coordinates.
  • ycoords, a list of y-coordinates.
  You can combine two arguments into a matrix with two columns (each list becomes a column of the matrix).
• power_regression_plot(xcoords,ycoords) draws the best fit power function, and puts the equation and R² value above the graph.

Example

Note that in this case the R² value is 1, indicating that data points fall directly on the curve.