In [1]:
import numpy as np
import matplotlib.pyplot as plt
In [2]:
x = [1,3,4,-4]
x[1]-x[0]
Out[2]:
2
In [3]:
np.diff(x)
Out[3]:
array([ 2,  1, -8])
In [4]:
v = np.arange(0,11)
print(v)
print(np.diff(v))
print(np.diff(v,2))
print(np.diff(np.diff(v)))

[ 0  1  2  3  4  5  6  7  8  9 10]
[1 1 1 1 1 1 1 1 1 1]
[0 0 0 0 0 0 0 0 0]
[0 0 0 0 0 0 0 0 0]
In [5]:
x = np.linspace(-2,2,101)
print(len(x))
x

101
Out[5]:
array([-2.  , -1.96, -1.92, -1.88, -1.84, -1.8 , -1.76, -1.72, -1.68,
       -1.64, -1.6 , -1.56, -1.52, -1.48, -1.44, -1.4 , -1.36, -1.32,
       -1.28, -1.24, -1.2 , -1.16, -1.12, -1.08, -1.04, -1.  , -0.96,
       -0.92, -0.88, -0.84, -0.8 , -0.76, -0.72, -0.68, -0.64, -0.6 ,
       -0.56, -0.52, -0.48, -0.44, -0.4 , -0.36, -0.32, -0.28, -0.24,
       -0.2 , -0.16, -0.12, -0.08, -0.04,  0.  ,  0.04,  0.08,  0.12,
        0.16,  0.2 ,  0.24,  0.28,  0.32,  0.36,  0.4 ,  0.44,  0.48,
        0.52,  0.56,  0.6 ,  0.64,  0.68,  0.72,  0.76,  0.8 ,  0.84,
        0.88,  0.92,  0.96,  1.  ,  1.04,  1.08,  1.12,  1.16,  1.2 ,
        1.24,  1.28,  1.32,  1.36,  1.4 ,  1.44,  1.48,  1.52,  1.56,
        1.6 ,  1.64,  1.68,  1.72,  1.76,  1.8 ,  1.84,  1.88,  1.92,
        1.96,  2.  ])
In [6]:
print(len(x[0:-1]))
x[0:-1]

100
Out[6]:
array([-2.  , -1.96, -1.92, -1.88, -1.84, -1.8 , -1.76, -1.72, -1.68,
       -1.64, -1.6 , -1.56, -1.52, -1.48, -1.44, -1.4 , -1.36, -1.32,
       -1.28, -1.24, -1.2 , -1.16, -1.12, -1.08, -1.04, -1.  , -0.96,
       -0.92, -0.88, -0.84, -0.8 , -0.76, -0.72, -0.68, -0.64, -0.6 ,
       -0.56, -0.52, -0.48, -0.44, -0.4 , -0.36, -0.32, -0.28, -0.24,
       -0.2 , -0.16, -0.12, -0.08, -0.04,  0.  ,  0.04,  0.08,  0.12,
        0.16,  0.2 ,  0.24,  0.28,  0.32,  0.36,  0.4 ,  0.44,  0.48,
        0.52,  0.56,  0.6 ,  0.64,  0.68,  0.72,  0.76,  0.8 ,  0.84,
        0.88,  0.92,  0.96,  1.  ,  1.04,  1.08,  1.12,  1.16,  1.2 ,
        1.24,  1.28,  1.32,  1.36,  1.4 ,  1.44,  1.48,  1.52,  1.56,
        1.6 ,  1.64,  1.68,  1.72,  1.76,  1.8 ,  1.84,  1.88,  1.92,
        1.96])
In [7]:
f = x**2
df = np.diff(f)
print(len(f))
print(len(df))

plt.plot(x,f,label='f')
plt.plot(x[0:-1],df,'r',label='df')

plt.grid()
plt.axis([-2,2,-1,2])
plt.legend()
plt.show()

101
100