问题
I wrote the following code to perform a spline interpolation:
import numpy as np
import scipy as sp
x1 = [1., 0.88, 0.67, 0.50, 0.35, 0.27, 0.18, 0.11, 0.08, 0.04, 0.04, 0.02]
y1 = [0., 13.99, 27.99, 41.98, 55.98, 69.97, 83.97, 97.97, 111.96, 125.96, 139.95, 153.95]
x = np.array(x1)
y = np.array(y1)
new_length = 25
new_x = np.linspace(x.min(), x.max(), new_length)
new_y = sp.interpolate.interp1d(x, y, kind='cubic')(new_x)
but I am getting:
ValueError: A value in x_new is below the interpolation range.
in interpolate.py
Any help would be appreciated.
回答1:
From the scipy documentation on scipy.interpolate.interp1d:
scipy.interpolate.interp1d(x, y, kind='linear', axis=-1, copy=True, bounds_error=True, fill_value=np.nan)
x : array_like. A 1-D array of monotonically increasing real values.
...
The problem is that the x values are not monotonically increasing. In fact they are monotonically decreasing. Let me know if this works and if its still the computation you are looking for.:
import numpy as np
import scipy as sp
from scipy.interpolate import interp1d
x1 = sorted([1., 0.88, 0.67, 0.50, 0.35, 0.27, 0.18, 0.11, 0.08, 0.04, 0.04, 0.02])
y1 = [0., 13.99, 27.99, 41.98, 55.98, 69.97, 83.97, 97.97, 111.96, 125.96, 139.95, 153.95]
new_length = 25
new_x = np.linspace(x.min(), x.max(), new_length)
new_y = sp.interpolate.interp1d(x, y, kind='cubic')(new_x)
回答2:
You can get this in the following way:
import numpy as np
import scipy as sp
from scipy.interpolate import interp1d
x1 = [1., 0.88, 0.67, 0.50, 0.35, 0.27, 0.18, 0.11, 0.08, 0.04, 0.04, 0.02]
y1 = [0., 13.99, 27.99, 41.98, 55.98, 69.97, 83.97, 97.97, 111.96, 125.96, 139.95, 153.95]
# Combine lists into list of tuples
points = zip(x1, y1)
# Sort list of tuples by x-value
points = sorted(points, key=lambda point: point[0])
# Split list of tuples into two list of x values any y values
x1, y1 = zip(*points)
new_length = 25
new_x = np.linspace(min(x1), max(x1), new_length)
new_y = sp.interpolate.interp1d(x1, y1, kind='cubic')(new_x)
来源：https://stackoverflow.com/questions/11851770/spline-interpolation-with-python