Python: Trying to run a function multiple times and save values for each run

Question

I am trying to get some data from a numerical simulation I am running. I have a function that solves my ODE and saves the values I need in a vector, rv . I would like to run my function 1000 times and get the mean value of rv for each timestep but I can't figure out how to do it.

My first thought was to call the function 1000 times and save the data in an array.

for i in range(1000):
    datavector = np.array(0)
    circle(N,dt,x0,y0,phi0,r,T,nu,v,Omega,R)
    datavector = np.append(datavector, rv)

But when I do that I got the following error message: NameError: name 'rv' is not defined

I'll attach my code since I'm not very good at explaining. Sorry for it being so messy

import math
import numpy as np
import matplotlib.pyplot as plt

def circle(N,dt,x0,y0,phi0,r,T,nu,v,Omega,R):


kB = 1.38*10**-23 # Boltzmann constant [J/K]plt #math constants
DT = kB*T/(6*math.pi*nu*r)  # Translational diffusion coefficent [m^2/s]
DR = kB*T/(8*math.pi*nu*r**3) # Rotational diffusion coefficent [rad^2/s]
n = 0 #iteration constant


x=x0 #vectors and initial values
y=y0
phi=phi0
phiv= np.array(phi) #vector containing phi-values
xv= np.array(x) #vector containing x-values
yv= np.array(y) #vector containing y-values
rv=np.array(np.sqrt(x**2+y**2))
xss=np.array(x) #vector containing start and (soon) end value
yss=np.array(y) # same as above

phiK=math.sqrt(2*DR*dt) #constants used in the iteration
xyK=math.sqrt(2*DT*dt)
Odt=Omega*dt

while n < N: #from 0 -> N-1
    phi = phi + Odt + phiK*np.random.normal(0,1) #eq (9)
    x = x + v*math.cos(phi)*dt + xyK*np.random.normal(0,1) #eq (10)
    y = y + v*math.sin(phi)*dt + xyK*np.random.normal(0,1) #eq (11)
    if (x**2+y**2) > R**2: #if the particle is outside the boundary
        if abs(x) > R: #need to make sure arccos(x/R) is meaningful
            xn = np.sign(x)*R
            theta = np.sign(y)*np.arccos((xn/R))#angle to particle
        else:
            theta = np.sign(y)*np.arccos((x/R))#angle to particle  
        rp = np.array([x,y]) #r for the particle
        rr = np.array([np.cos(theta)*R,np.sin(theta)*R]) #r for the boundary closest to the particle
        #d = rp - rr #smallest distance from particle to boundary
        q = (2*np.linalg.norm(rr)/np.linalg.norm(rp)) - 1
        x = q*np.array(rp[0]) #x- and y-value forced inside the boundary
        y = q*np.array(rp[1])

    phiv = np.append(phiv, phi) #adding all phi-values to a vector
    xv = np.append(xv, x) # adding all x-values to a vector
    yv = np.append(yv, y) # adding all y-values to a vector'
    rv = np.append(rv,(np.sqrt(x**2+y**2)))
    n=n+1 #iteration 


return(rv)
#print(rv)

for i in range(2): #run the program a number of times
    datavector = np.array(0)
    circle(1E5,1E-3,0*np.random.uniform(-1E-5,1E-5),0*np.random.uniform(-1E-5,1E-5),np.random.uniform(-2*np.pi,2*np.pi),1E-6,300,1E-3,5*1E-6,0,2E-5)
    datavector = np.append(datavector, rv)
np.savetxt('testet.txt', datavector)

Answer 1

name 'rv' is not defined means your variable has not been defined before operations have been done upon it.

From the information you provided, rv is never defined. On top of that, you are re-initialising your result vector datavector at every iteration, while it should only be initialised BEFORE your main loop.

I assume rv is the return value from circle .

So a correction of your code should look like:

datavector = []
for i in range(1000):
    rv = circle(N,dt,x0,y0,phi0,r,T,nu,v,Omega,R)
    datavector.append(rv)