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I have a larger, more complex function that essentially boils down to the below function: f(X). Why can't this function take in linspace integers as a parameter? This error is given:

"TypeError: only integer scalar arrays can be converted to a scalar index"

import numpy
from matplotlib import*
from numpy import*
import numpy as np
from math import*
import random
from random import *
import matplotlib.pyplot as plt

def f(x):

    for i in range(x):
        x+=1

    return x

xlist = np.linspace(0, 100, 10)

ylist = f(xlist)

plt.figure(num=0)
Stanley Smith
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    It's unclear to me what you are actually trying to do. It breaks because the range() function requires a scalar and you are passing a numpy array. I'm totally guessing, but I think maybe you want "for i in range(len(x))" instead, though then "x+=1" doesn't make a ton of sense unless that's just a placeholder for your actual function – pasnik Mar 23 '22 at 04:54
  • `range` is a python function that takes ONE number, not an array (of more than one elements). Did you look up `range`? `for i in x: print(i)`. But you can't modify `i` in the loop. `x = [i+1 for i in range(10)]` also works. – hpaulj Mar 23 '22 at 05:10
  • @pasnik I'm trying to call a function that uses a for-loop to compute something, draw x number of points on a plot, based on the range within the loop. I am quite new to numpy arrays, but I used this video: https://www.youtube.com/watch?v=ufO_BScIHDQ , and based on how he wrote the function it seemed like x was a scalar. – Stanley Smith Mar 23 '22 at 05:22
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    It's hard to learn programming from videos. It's all to easy to miss essential details. In some cases you might even want to check the comments; others might have had similar problems. Any ways, in the long run there's no substitute for reading the official program documentation, or at least having it at hand. In this case you need both `python` and `numpy`. – hpaulj Mar 23 '22 at 05:43
  • As you just started to learn to program, now is a good time to internalize that [`import *` is not good practice](https://stackoverflow.com/questions/2386714/why-is-import-bad). – Mr. T Mar 23 '22 at 07:38

3 Answers3

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linspace produces a numpy array, not a list. Don't confuse the two.

In [3]: x = np.linspace(0,100,10)
In [4]: x
Out[4]: 
array([  0.        ,  11.11111111,  22.22222222,  33.33333333,
        44.44444444,  55.55555556,  66.66666667,  77.77777778,
        88.88888889, 100.        ])

The numbers will look nicer if we take into account that linspace includes the end points:

In [5]: x = np.linspace(0,100,11)
In [6]: x
Out[6]: array([  0.,  10.,  20.,  30.,  40.,  50.,  60.,  70.,  80.,  90., 100.])

As an array, we can simply add a scalar; no need to write a loop:

In [7]: x + 1
Out[7]: array([  1.,  11.,  21.,  31.,  41.,  51.,  61.,  71.,  81.,  91., 101.])

range takes one number (or 3), but never an array (of more than 1 element):

In [8]: for i in range(5): print(i)
0
1
2
3
4

We can't modify i in such a loop, or the "x" used to create the range. But we can write a list comprehension:

In [9]: [i+1 for i in range(5)]
Out[9]: [1, 2, 3, 4, 5]

references:

https://www.w3schools.com/python/ref_func_range.asp

https://numpy.org/doc/stable/reference/generated/numpy.linspace.html

hpaulj
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xlist = np.linspace(0, 100, 10) + 1
paul-shuvo
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Based on your comment it seems you are just trying to plot a few points. I think your use of range and linspace are redundant and you don't need a loop at all. You do not need a for loop to plot many points, unless you are trying to plot multiple curves or do something fancy with each point. For example, this plots 10 points:

x = np.linspace(0, 100, 10)
y=x*x
plt.plot(x,y,'.')

I think this is a good place to start: https://matplotlib.org/3.5.1/tutorials/introductory/pyplot.html

pasnik
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