Defining function using loop for numpy.linspace

Question

I am a beginner at programming, I am using python 3.0

I am given a function h(x) = 1 if 0.1<= x <= 0.3 , or = 0 otherwise

I have

L = 1
N=200    
x = numpy.linspace(0,L,N)

I want to define a function for h(x) that loops through the values of x and returns 1 or 0 based on the conditions given above

Answer 1

You can use np.logical_and and astype :

np.logical_and(x >= 0.1, x <= 0.3).astype(int)

---

Plot showing the behavior:

Answer 2

You can use a list comprehension as following. This is basically using a combination of for loop, if-else statement in a one liner. Here, you use if condition to check if x is between 0.1 and 0.3 and saves 1 in the hx otherwise 0.

import numpy
import matplotlib.pyplot as plt
L = 1
N=200    
x = numpy.linspace(0,L,N)
hx = [1 if 0.1 <= i <= 0.3 else 0 for i in x] # list comprehension
plt.plot(x, hx)
plt.xlabel('x', fontsize=18)
plt.ylabel('h(x)', fontsize=18)

Alternative vectorised approach : Here (x>=0.1) & (x<=0.3) returns the indices where x fulfills the conditions and for those indices, evaluate hx to 1. Here you initialize hx to be all zeros.

hx = numpy.zeros(N)
hx[(x>=0.1) & (x<=0.3)] = 1

Using it as a function

def get_hx(x):
    # hx = numpy.zeros(N)
    # hx[(x>=0.1) & (x<=0.3)] = 1
    hx = [1 if 0.1 <= i <= 0.3 else 0 for i in x]
    return hx

hx = get_hx(x)