import numpy from sklearn.metrics import r2_score x = [1,2,3,5,6,7,8,9,10,12,13,14,15,16,18,19,21,22] y = [100,90,80,60,60,55,60,65,70,70,75,76,78,79,90,99,99,100] mymodel = numpy.poly1d(numpy.polyfit(x, y, 3)) print(r2_score(y, mymodel(x)))