calculate the mean of every nth list in a list of lists using a loop

Question

I am trying to calculate the mean of every nth list in a list of lists using a loop. I have been able to do so without a loop, but this will prove laborious to do when the list of lists gets longer.

Im struggling to explain this so heres the code

import numpy as np
import matplotlib.pyplot as plt 


list = []
t_r = np.arange(0,8)
i = 0
a =[[0.98,1.93,2.99,4.01,4.92,6.00,7.08,7.67, 8.00],[0,0,0,1,2,3,3,2,3],[0.93,1.99,2.99,3.91,4.82,6.03,7.01,8.00],[0,1,2,3,4,5,5,6],[0.88,2.09,3.01,4.11,5.65,7.12,8.00],[4,5,6,7,8,7,6]]
#########################
for t in t_r:
    b1 = np.array(a[0]) <= t
    b2 = np.array(a[2]) <= t 
    b3 = np.array(a[4]) <= t 

    ind1 = [(np.count_nonzero(b1))]
    ind2 = [(np.count_nonzero(b2))]
    ind3 = [(np.count_nonzero(b3))]

    x1 = np.array(a[1])
    x_mean1 = x1[ind1]
    x2 = np.array(a[3])
    x_mean2 = x2[ind2]
    x3 = np.array(a[5])
    x_mean3 = x3[ind2]

    x_mean_list = [x_mean1, x_mean2, x_mean3]
    x_average = np.mean(x_mean_list)    
    list.append(x_average)
#########################



no_of_sim = 3
counter = 0
while counter <= ((no_of_sim*2)-1):
    plt.plot(a[counter],a[counter+1], lw = 0.5)
    plt.plot(list, color = "black")
    plt.plot(x_average)
    plt.xlabel('Time (s)')
    plt.ylabel('copy no.')
    counter += 2
plt.show()

The bit inbetween the hashtags is the bit I'm trying to write a loop for so I don't have to manually change it when the list if lists gets much longer

Answer 1

Your code between the hashes are equivalent to the following:

data = [np.array(x) for x in a[::2]]
idx = [np.array(x) for x in a[1::2]]

lst = [np.mean([x[(d<=t).sum()] for x,d in zip(idx,data)]) for t in t_r ]

Output:

[1.3333333333333333,
 2.0,
 2.3333333333333335,
 3.3333333333333335,
 4.0,
 5.333333333333333,
 5.0,
 5.0]

Answer 2

check out this code:

a =[[0.98,1.93,2.99,4.01,4.92,6.00,7.08,7.67, 8.00],[0,0,0,1,2,3,3,2,3],[0.93,1.99,2.99,3.91,4.82,6.03,7.01,8.00],[0,1,2,3,4,5,5,6],[0.88,2.09,3.01,4.11,5.65,7.12,8.00],[4,5,6,7,8,7,6]]

i = 0
for li in a:
    print("Mean of list at index", i, "is:", sum(li)/len(li))
    i += 1