Modelling Population with Stochastic Model and a Random Variable





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So I have this stochastic model: N(t+1)=(1+r^3)N(t), where r is a random variable from a Normal Population with mean= -0.1 and standard deviation=0.2.



I'm trying to make a histogram from 1000 samples of this random that will model my population, and I've tried a few things to no avail.



So far I have:



import numpy as np 

import numpy.random as npr 

import matplotlib.pyplot as plt 

npr.seed(101)



N = np.zeros(11)

N[0]=100

tvec = np.arange(0, 10, 0.1)

r = npr.normal(loc=2,scale=3, size=1000)



for t in tvec[:10]:

    N[t+1]=(1+r**3)+N[t]



plt.hist(N)


but that gives me an error.




IndexError: only integers, slices (:), ellipsis (...),
numpy.newaxis (None) and integer or boolean arrays are valid indices




Which tells me that I'm not able to take the random numbers I'm sampling and use them in my equation.



So, I'm wondering if there's a different way I could be going about this?



Thanks in advance!






python python-3.x







share|improve this question























  • Could you point out the line which threw that error please?

    – Arthur-1
    Nov 29 '18 at 4:03











  • @Arthur-1 it was N[t+1]=(1+r**3)+N[t]

    – dejsdukes
    Nov 29 '18 at 4:06


















2















So I have this stochastic model: N(t+1)=(1+r^3)N(t), where r is a random variable from a Normal Population with mean= -0.1 and standard deviation=0.2.



I'm trying to make a histogram from 1000 samples of this random that will model my population, and I've tried a few things to no avail.



So far I have:



import numpy as np 

import numpy.random as npr 

import matplotlib.pyplot as plt 

npr.seed(101)



N = np.zeros(11)

N[0]=100

tvec = np.arange(0, 10, 0.1)

r = npr.normal(loc=2,scale=3, size=1000)



for t in tvec[:10]:

    N[t+1]=(1+r**3)+N[t]



plt.hist(N)


but that gives me an error.




IndexError: only integers, slices (:), ellipsis (...),
numpy.newaxis (None) and integer or boolean arrays are valid indices




Which tells me that I'm not able to take the random numbers I'm sampling and use them in my equation.



So, I'm wondering if there's a different way I could be going about this?



Thanks in advance!






python python-3.x







share|improve this question























  • Could you point out the line which threw that error please?

    – Arthur-1
    Nov 29 '18 at 4:03











  • @Arthur-1 it was N[t+1]=(1+r**3)+N[t]

    – dejsdukes
    Nov 29 '18 at 4:06














2












2








2








So I have this stochastic model: N(t+1)=(1+r^3)N(t), where r is a random variable from a Normal Population with mean= -0.1 and standard deviation=0.2.



I'm trying to make a histogram from 1000 samples of this random that will model my population, and I've tried a few things to no avail.



So far I have:



import numpy as np 

import numpy.random as npr 

import matplotlib.pyplot as plt 

npr.seed(101)



N = np.zeros(11)

N[0]=100

tvec = np.arange(0, 10, 0.1)

r = npr.normal(loc=2,scale=3, size=1000)



for t in tvec[:10]:

    N[t+1]=(1+r**3)+N[t]



plt.hist(N)


but that gives me an error.




IndexError: only integers, slices (:), ellipsis (...),
numpy.newaxis (None) and integer or boolean arrays are valid indices




Which tells me that I'm not able to take the random numbers I'm sampling and use them in my equation.



So, I'm wondering if there's a different way I could be going about this?



Thanks in advance!






python python-3.x







share|improve this question














So I have this stochastic model: N(t+1)=(1+r^3)N(t), where r is a random variable from a Normal Population with mean= -0.1 and standard deviation=0.2.



I'm trying to make a histogram from 1000 samples of this random that will model my population, and I've tried a few things to no avail.



So far I have:



import numpy as np 

import numpy.random as npr 

import matplotlib.pyplot as plt 

npr.seed(101)



N = np.zeros(11)

N[0]=100

tvec = np.arange(0, 10, 0.1)

r = npr.normal(loc=2,scale=3, size=1000)



for t in tvec[:10]:

    N[t+1]=(1+r**3)+N[t]



plt.hist(N)


but that gives me an error.




IndexError: only integers, slices (:), ellipsis (...),
numpy.newaxis (None) and integer or boolean arrays are valid indices




Which tells me that I'm not able to take the random numbers I'm sampling and use them in my equation.



So, I'm wondering if there's a different way I could be going about this?



Thanks in advance!






python python-3.x




python python-3.x






share|improve this question













share|improve this question











share|improve this question




share|improve this question










asked Nov 29 '18 at 3:54









dejsdukesdejsdukes

536




536













  • Could you point out the line which threw that error please?

    – Arthur-1
    Nov 29 '18 at 4:03











  • @Arthur-1 it was N[t+1]=(1+r**3)+N[t]

    – dejsdukes
    Nov 29 '18 at 4:06



















  • Could you point out the line which threw that error please?

    – Arthur-1
    Nov 29 '18 at 4:03











  • @Arthur-1 it was N[t+1]=(1+r**3)+N[t]

    – dejsdukes
    Nov 29 '18 at 4:06

















Could you point out the line which threw that error please?

– Arthur-1
Nov 29 '18 at 4:03





Could you point out the line which threw that error please?

– Arthur-1
Nov 29 '18 at 4:03













@Arthur-1 it was N[t+1]=(1+r**3)+N[t]

– dejsdukes
Nov 29 '18 at 4:06





@Arthur-1 it was N[t+1]=(1+r**3)+N[t]

– dejsdukes
Nov 29 '18 at 4:06












1 Answer
1






active

oldest

votes


















1














The error occurs because t is a float and initially has a value of 0.0. If you try N[0.0] you can reproduce the error. You can use integers rather than floats. Also, I changed r to r_values and zipped it to t so the loop works only on single values for r and t rather than an array for r.



import numpy as np

import numpy.random as npr

import matplotlib.pyplot as plt



npr.seed(101)



N = np.zeros(11)

N[0]=100

tvec = np.arange(0, 10, 1)

r_values = npr.normal(loc=2,scale=3, size=10)



for t,r in zip(tvec, r_values):

    #print(t,r)

    N[t+1]=(1+r**3)+N[t]



plt.hist(N)


enter image description here






share|improve this answer





















  • 1





    ah thank you! I appreciate it

    – dejsdukes
    Nov 29 '18 at 5:01












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1 Answer
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1 Answer
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active

oldest

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votes









1














The error occurs because t is a float and initially has a value of 0.0. If you try N[0.0] you can reproduce the error. You can use integers rather than floats. Also, I changed r to r_values and zipped it to t so the loop works only on single values for r and t rather than an array for r.



import numpy as np

import numpy.random as npr

import matplotlib.pyplot as plt



npr.seed(101)



N = np.zeros(11)

N[0]=100

tvec = np.arange(0, 10, 1)

r_values = npr.normal(loc=2,scale=3, size=10)



for t,r in zip(tvec, r_values):

    #print(t,r)

    N[t+1]=(1+r**3)+N[t]



plt.hist(N)


enter image description here






share|improve this answer





















  • 1





    ah thank you! I appreciate it

    – dejsdukes
    Nov 29 '18 at 5:01
















1














The error occurs because t is a float and initially has a value of 0.0. If you try N[0.0] you can reproduce the error. You can use integers rather than floats. Also, I changed r to r_values and zipped it to t so the loop works only on single values for r and t rather than an array for r.



import numpy as np

import numpy.random as npr

import matplotlib.pyplot as plt



npr.seed(101)



N = np.zeros(11)

N[0]=100

tvec = np.arange(0, 10, 1)

r_values = npr.normal(loc=2,scale=3, size=10)



for t,r in zip(tvec, r_values):

    #print(t,r)

    N[t+1]=(1+r**3)+N[t]



plt.hist(N)


enter image description here






share|improve this answer





















  • 1





    ah thank you! I appreciate it

    – dejsdukes
    Nov 29 '18 at 5:01














1












1








1







The error occurs because t is a float and initially has a value of 0.0. If you try N[0.0] you can reproduce the error. You can use integers rather than floats. Also, I changed r to r_values and zipped it to t so the loop works only on single values for r and t rather than an array for r.



import numpy as np

import numpy.random as npr

import matplotlib.pyplot as plt



npr.seed(101)



N = np.zeros(11)

N[0]=100

tvec = np.arange(0, 10, 1)

r_values = npr.normal(loc=2,scale=3, size=10)



for t,r in zip(tvec, r_values):

    #print(t,r)

    N[t+1]=(1+r**3)+N[t]



plt.hist(N)


enter image description here






share|improve this answer















The error occurs because t is a float and initially has a value of 0.0. If you try N[0.0] you can reproduce the error. You can use integers rather than floats. Also, I changed r to r_values and zipped it to t so the loop works only on single values for r and t rather than an array for r.



import numpy as np

import numpy.random as npr

import matplotlib.pyplot as plt



npr.seed(101)



N = np.zeros(11)

N[0]=100

tvec = np.arange(0, 10, 1)

r_values = npr.normal(loc=2,scale=3, size=10)



for t,r in zip(tvec, r_values):

    #print(t,r)

    N[t+1]=(1+r**3)+N[t]



plt.hist(N)


enter image description here







share|improve this answer














share|improve this answer



share|improve this answer








edited Nov 29 '18 at 4:49

























answered Nov 29 '18 at 4:36









DodgeDodge

1,50211023




1,50211023








  • 1





    ah thank you! I appreciate it

    – dejsdukes
    Nov 29 '18 at 5:01














  • 1





    ah thank you! I appreciate it

    – dejsdukes
    Nov 29 '18 at 5:01








1




1





ah thank you! I appreciate it

– dejsdukes
Nov 29 '18 at 5:01





ah thank you! I appreciate it

– dejsdukes
Nov 29 '18 at 5:01




















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