[英]I'm trying to define a function an its derivative but it seems to not be working
所以我想编写代码以使用近似的数值方法,并且我需要函数及其导数,所以我这样做了:
import numpy as np
import sympy as sym
import math
x = Symbol('x')
fx = lambda x:math.tan(2*(x-5*math.pi/2))-x
f = math.tan(2*(x-5*math.pi/2))-x
dfx = lambdify (x,f.diff(x))
这是错误,它在我使用多项式函数之前有效:
TypeError Traceback (most recent call last)
<ipython-input-18-e3f579396c41> in <module>
1 # INGRESO
2 fx = lambda x:math.tan(2*(x-5*math.pi/2))-x
----> 3 f = (float)(math.tan(2*(x-5*math.pi/2))-x)
4 dfx = lambdify (x,f.diff(x))
5
~\Anaconda3\lib\site-packages\sympy\core\expr.py in __float__(self)
278 if result.is_number and result.as_real_imag()[1]:
279 raise TypeError("can't convert complex to float")
--> 280 raise TypeError("can't convert expression to float")
281
282 def __complex__(self):
类型错误:无法将表达式转换为浮点数
您应该使用例如sympy.tan
而不是math.tan
。 math.tan
函数只接受float
输入,并且您传入的是符号 SymPy 表达式。
In [10]: import numpy as np
...: import sympy as sym
...: import math
...: x = Symbol('x')
...: fx = lambda x:sym.tan(2*(x-5*sym.pi/2))-x
...: f = sym.tan(2*(x-5*sym.pi/2))-x
...: dfx = lambdify (x,f.diff(x))
In [11]: dfx(1)
Out[11]: 10.548798408083835
使用 sympi tan 和 pi:math 库不适用于 sympy
import sympy as sym
from sympy import tan,pi
import numpy as np
x = sym.Symbol('x')
fx = tan(2*(x-5*pi/2))-x
dfx = sym.lambdify (x,fx)
这工作...
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