So I am trying to plot a graph of 3 of my functions for a beam on one graph using the matplotlib module and am getting value errors when attempting to do so. The main bulk of code is:
class beam(object):
'''This class is models the deflection of a simply supported beam under
multiple point loads, following Euler-Bernoulli theory and the principle
of superposition
'''
def __init__(self, E, I, L):
'''The class costructor
'''
self.E = E # Young's modulus of the beam in N/m^2
self.I = I # Second moment of area of the beam in m^4
self.L = L # Length of the beam in m
self.Loads = [(0.0, 0.0)] # the list of loads applied to the beam
def setLoads(self, Loads):
'''This function allows multiple point loads to be applied to the beam
using a list of tuples of the form (load, position)
'''
self.Loads = Loads
def beamDeflection(self, Load, x):
"""Calculate the deflection at point x due to application of single
load
"""
Force, distanceA = Load #P1 = Force , a = distanceA
E = self.E
I = self.I
L = self.L
distanceB = L - distanceA
i = (Force*distanceB)/(6*L*E*I)
j = ((L/distanceB)*(x-distanceA)**3 - x**3 + (L**2 - distanceB**2)*x)
k = (Force*distanceB*x)/(6*L*E*I)
l = (L**2 - x**2 - distanceB**2)
if x > distanceA:
return i*j
else:
return k*l
def getTotalDeflection(self, x):
"""Calculate total deflection of beam due to multiple loads
"""
#return sum(self.beamDeflection(loadall, x) for loadall in self.Loads)
return sum(self.beamDeflection(load, x) for load in self.Loads)
def getSlope(self, x):
"""Calculate gradient at a point x on beam due to deflection
"""
V = lambda x: self.getTotalDeflection(x)
return scipy.misc.derivative(V, x, dx = 10**-6)
def getMoment(self, x):
"""Calculate bending moment at a point x on beam
"""
E = self.E
I = self.I
W1 = lambda x: self.getSlope(x)
W2 = scipy.misc.derivative(W1, x, dx = 10**-6)
return (-1*E*I)*W2
def plotBeamData(self, xs):
"""Plot deflection, slope and bending moment against position x for a
list of floats or numpy.array xs describing positions along beam
"""
deflection = self.getTotalDeflection(xs)
slope = self.getSlope(xs)
moment = self.getMoment(xs)
matplotlib.pyplot.plot(xs, deflection, 'b', label = "deflection (mm)")
matplotlib.pyplot.plot(xs, slope, 'g', label = "slope (mm/m)")
matplotlib.pyplot.plot(xs, moment, 'r', label = "moment (kNm)")
matplotlib.pyplot.xlabel("Distance along beam (m)")
matplotlib.pyplot.ylabel("Value in units")
matplotlib.pyplot.show()
This is the section of code from the class shown above, I am getting an error when trying to run:
def plotBeamData(self, xs):
...
An example input would be:
>>> b = beam(8.0E9, 1.333E-4, 5.0)
>>> b.setLoads([(900, 3.1), (700, 3.8), (1000, 4.2)])
>>> xs = numpy.linspace(0,5,500)
>>> b.plotBeamData(xs)
The error I am receiving is:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "C:/Users/Dag/Downloads/beamModel.py", line 93, in plotBeamData
deflection = self.getTotalDeflection(xs)
File "C:/Users/Dag/Downloads/beamModel.py", line 60, in getTotalDeflection
return sum(self.beamDeflection(load, x) for load in self.Loads)
File "C:/Users/Dag/Downloads/beamModel.py", line 60, in <genexpr>
return sum(self.beamDeflection(load, x) for load in self.Loads)
File "C:/Users/Dag/Downloads/beamModel.py", line 50, in beamDeflection
if x > distanceA:
ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()
I had previously just changed the code changing it from deflection = self.getTotalDeflection, which was giving me a value error about x and y must be in the same dimension, to deflection = self.getTotalDeflection(xs) which is now giving me a new error. Grateful for any help, really stuck. Thanks.
