How to draw a polynomial curve in matplotlib python?

Question

I'm trying to draw a curve for regression fitting. The curve is for a higher degree polynomial ( 6 and above ).

fig=figure()
ax1=fig.add_axes((0.1,0.2,0.8,0.7))
ax1.set_title("Training data(blue) and fitting curve(red)")
ax1.set_xlabel('X-axis')
ax1.set_ylabel('Y-axis')

ax1.plot(x_train,y_train,'.',x_train,np.polyval(best_coef,x_train),'-r') 
show()

This is the output of the given code

I want it to be a smooth curve.

something like this , with a continues red line , instead of discreet point of red

i've written a polyfit function which returns the coefficient of best degree polynomial that fits the data. — ajithalbus
– ajithalbus, Commented Aug 18, 2017 at 7:16

ml4294 · Accepted Answer · 2017-08-17 19:09:58Z

1

I think you just need to sort x_train before plotting the fit results:

ax1.plot(x_train,y_train,'.', np.sort(x_train),np.polyval(best_coef,np.sort(x_train)),'-r')

The plot you included looks like the x_train values (and therefore also the fitted values) are in random order, but the plot routine does not connect the nearest points, but consecutive points in the arrays.

answered Aug 17, 2017 at 19:09

ml4294

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