Forming array from for loop output

Question

I have the following

import math
import matplotlib.pyplot as plt

def nraphson(fn, dfn, x, tol, maxiter):
    for i in range(maxiter):
        xnew = x - fn(x)/dfn(x)
        if abs(xnew - x) < tol: break
        x = xnew
    return xnew, i

y = lambda x: math.exp(x) - x**2
dy = lambda x: math.exp(x) - 2*x
x, n = nraphson(y, dy, j, 10**-5, 100)
guess = range(-10,6)
for j in guess:
    print(nraphson(y, dy, j, 10**-5, 100))

my output is of the form

(-0.7034674225098828, 6)
(-0.7034674224990228, 6)
(-0.7034674224984084, 6)
(-0.7034674224983918, 6)
(-0.7034674224983917, 6)
(-0.703467422509882, 5)
(-0.7034674224984084, 5)
(-0.7034674224983917, 5)
(-0.7034674224984067, 4)
(-0.7034674224983924, 3)
(-0.7034674224983924, 4)
(-0.7034674224983917, 5)
(-0.7034674224983917, 6)
(-0.7034674224983917, 6)
(-0.7034674224984245, 8)
(-0.7034674224983917, 10)

I am attempting to isolate the second number from my output to form a list or array to us to plot a graph, how can I adjust my code as to give me a list or array like the following?

[6, 6, 6, 6, 6, 5, 5, 5, 4, 3, 4, 5, 6, 6, 8, 10]

David Miró · Accepted Answer · 2021-10-15 13:49:20Z

1

Try this:

...
guess = range(-10,6)
result = [nraphson(y, dy, j, 10**-5, 100)[1] for j in guess]
print(result)

answered Oct 15, 2021 at 13:49

David Miró

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Comments

at54321 · Accepted Answer · 2021-10-15 13:46:37Z

1

If you just want to print the second values, in the for loop at the end:

for j in guess:
    print(nraphson(y, dy, j, 10**-5, 100)[1])

In your code you were printing the result of nraphson(y, dy, j, 10**-5, 100), which is a tuple with two elements. To get the second element, just access it with [1].

If you don't want to print the values but want to create a list with those values, simply do something like this:

tuples = [nraphson(y, dy, j, 10**-5, 100) for j in guess]
second_nums = [t[1] for t in tuples]

answered Oct 15, 2021 at 13:46

at54321

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Comments

user2668284 · Accepted Answer · 2021-10-15 13:50:16Z

1

Replace the last two lines of your code with this:

L = [nraphson(y, dy, j, 10**-5, 100)[1] for j in guess]
print(L)

answered Oct 15, 2021 at 13:50

user2668284

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