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Interpolation and Extrapolation in 2D in Python

Learn how to interpolation and extrapolate data in two dimensions

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Imports

The tutorial below imports NumPy, Pandas, and SciPy.

In [1]:
import plotly.plotly as py
import plotly.graph_objs as go
from plotly.tools import FigureFactory as FF

import numpy as np
import pandas as pd
import scipy

Tips

Interpolation refers to the process of generating data points between already existing data points. Extrapolation is the process of generating points outside a given set of known data points.
(inter and extra are derived from Latin words meaning 'between' and 'outside' respectively)

Spline Interpolation

Interpolate for a set of points and generate the curve of best fit that intersects all the points.

In [2]:
from scipy import interpolate

x = np.arange(-5.0, 5.0, 0.25)
y = np.arange(-5.0, 5.0, 0.25)
xx, yy = np.meshgrid(x, y)
z = np.sin(xx**2+yy**2)
f = interpolate.interp2d(x, y, z, kind='cubic')

xnew = np.arange(-5.0, 5.0, 1e-1)
ynew = np.arange(-5.0, 5.0, 1e-1)
znew = f(xnew, ynew)

trace1 = go.Scatter3d(
    x=x,
    y=y,
    z=z[0, :],
    mode='markers',
    name='Data',
    marker = dict(
        size = 7
    )
)

trace2 = go.Scatter3d(
    x=ynew,
    y=xnew,
    z=znew[0, :],
    marker=dict(
        size=3,
    ),
    name='Interpolated Data'
)

layout = go.Layout(
    title='Interpolation and Extrapolation in 2D',
    scene=dict(
            camera= dict(
                up=dict(x=0, y=0, z=1),
                center=dict(x=0, y=0, z=0),
                eye=dict(x=1, y=-1, z=0)
            )
    )
)

data = [trace1, trace2]

fig = go.Figure(data=data, layout=layout)
py.iplot(fig, filename='interpolation-and-extrapolation-2d')
Out[2]:
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