我需要计算和绘制一个函数,它是前两个导数。然后,我需要在图表上绘制原始函数的最小和最大点。我已经计算了这些,但是对于如何绘制数据图形却迷失了。最小/最大点的x值为criticalPoints[]
y值为
criticalPointsY[]
这是出现错误的代码段。
equation=CreateFunction();
firstDeriv=equation.diff(x);
secondDeriv=firstDeriv.diff(x);
print(equation);
criticalPoints=solveset(firstDeriv,x);
criticalPointsY=[];
for a in criticalPoints:
criticalPointsY.append(equation.subs(x,a));
p=plot(equation,firstDeriv,secondDeriv,(x,-10,10));
# Need to add the critical points to the graph. We have them, and the
# y values, but need to put them on the graphs.
print(criticalPoints)
print(criticalPointsY);
for a in range(0, len(criticalPoints)):
xval=criticalPoints[a];
yval=criticalPointsY[a];
plt.plot(xval, yval, 'ro')
p.show();
plt.show();
运行程序时,出现此错误。`
Traceback (most recent call last):
File "--------", line 58, in <module>
xval=criticalPoints[a];
TypeError: 'FiniteSet' object does not support indexing
我尝试在p上绘制点并得到不同的错误
p.plot(criticalPoints,criticalPointsY);
AttributeError: 'Plot' object has no attribute 'plot'
有没有办法在此图上绘制点?(p)
我已经解决了这个问题。由于方程的导数可能不存在,或者水平线,因此出现了难题。
x = symbols('x')
UserInput()
equation = CreateFunction()
firstDeriv = equation.diff(x)
secondDeriv = firstDeriv.diff(x)
workingEquations=[]
hasEquations=False
我在此部分所做的是通过将方程式转换为字符串并查看是否存在x值来进行测试。如果存在,则将方程式附加到稍后将访问的数组中,否则,将绘制水平线。我还翻了个布尔,稍后再告诉我们是否有一个带变量的方程。
if(not str(equation).find("x")==-1):
workingEquations.append(equation)
hasEquations=True
print("True")
else:
plt.axhline(y=equation)
if(not str(firstDeriv).find("x")==-1):
workingEquations.append(firstDeriv)
else:
plt.axhline(y=firstDeriv)
if(not str(secondDeriv).find("x")==-1):
workingEquations.append(secondDeriv)
else:
plt.axhline(y=secondDeriv)
try:
criticalPoints = list(solveset(firstDeriv, x))
criticalPointsY = [equation.subs(x, a) for a in criticalPoints]
plt.plot(criticalPoints, criticalPointsY, 'k*')
except:
print("No critical points")
如果我们有方程式,则可以从该数组中绘制出它们的图形,并在其中附加所有非水平方程式。
if(hasEquations):
xx = np.linspace(-10, 10, 1000)
yy = lambdify(x, workingEquations)(xx)
plt.plot(xx, np.transpose(yy))
plt.show()
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