How do I get a boolean array from an array A with multiple conditions in python?

A = np.arange(0,20,1)
A<7

The above code will return a boolean array where its elements are true when A<7 and otherwise false. How do I get such a boolean array for x < A < 7?

If your x = 3, then:

a = np.arange(0,20,1)
a
array([ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15, 16,
       17, 18, 19])

(a>3) & (a<7)
array([False, False, False, False,  True,  True,  True, False, False,
       False, False, False, False, False, False, False, False, False,
       False, False])

If you want an or condition you can replace & with |:

(a<3) | (a>7) #Less than 3 or greater than 7
array([ True,  True,  True, False, False, False, False, False,  True,
        True,  True,  True,  True,  True,  True,  True,  True,  True,
        True,  True])

How to use NumPy where with multiple conditions in Python, Call numpy. where(condition) with condition as multiple boolean expressions involving the array combined using | (or) or & (and). Use arr[x] with x as the previous results to get a new array containing only the elements of arr for which each conditions is True . Boolean Values. In programming you often need to know if an expression is True or False. You can evaluate any expression in Python, and get one of two answers, True or False. When you compare two values, the expression is evaluated and Python returns the Boolean answer:

Choose x value and then :

x = 3
np.logical_and(x<A, A<7)

How to filter a NumPy array based on two conditions in Python, Use a mask and array indexing to filter the array based on two conditions. A mask is an array of boolean values that each correspond to a value in the original� Python's cascaded if statement: test multiple conditions after each other. Python's cascaded if statement evaluates multiple conditions in a row. When one is True, that code runs. If all are False the else code executes. Compare values with Python's if statements: equals, not equals, bigger and smaller than. Python's if statements can compare

Just use a list comprehension:

x = 3
bools = [i<7 and i> x for i in A]

Python Numpy : Select elements or indices by conditions from , Here we need to check two conditions i.e. element > 5 and element < 20. But python keywords and , or doesn't works with bool Numpy Arrays. This section covers the use of Boolean masks to examine and manipulate values within NumPy arrays. Masking comes up when you want to extract, modify, count, or otherwise manipulate values in an array based on some criterion: for example, you might wish to count all values greater than a certain value, or perhaps remove all outliers that are above some threshold.

You could use numpy.logical_and for that task, example:

import numpy as np
A = np.arange(0,20,1)
B = np.logical_and(3<A,A<7)
print(B)

Output:

[False False False False  True  True  True False False False False False
 False False False False False False False False]

Boolean Masking of Arrays, The results of these tests are the Boolean elements of the result array. Of course, it is also 188, 77, 188]). Indices can appear in every order and multiple times! Using loc with multiple conditions. loc is used to Access a group of rows and columns by label(s) or a boolean array. As an input to label you can give a single label or it’s index or a list of array of labels. Enter all the conditions and with & as a logical operator between them

import timeit

A = np.arange(0, 20, 1)
# print(A)
x = 3


def fun():
    return [x < i < 7 for i in A]


def fun2():
    return (A < 7) & (A > 3)


def fun3():
    return np.logical_and(x < A, A < 7)

def fun4():
    return [i < 7 and i > x for i in A]


print('fun()', timeit.timeit('fun()', number=10000, globals=globals()))
print('fun2()', timeit.timeit('fun2()', number=10000, globals=globals()))
print('fun3()', timeit.timeit('fun3()', number=10000, globals=globals()))
print('fun4()', timeit.timeit('fun4()', number=10000, globals=globals()))

output:

execution time(in seconds):

fun() 0.055701432000205386
fun2() 0.016561345997615717
fun3() 0.016588653001235798
fun4() 0.0446821750010713

NumPy: Select indices satisfying multiple conditions in a NumPy array, NumPy Array Object Exercises, Practice and Solution: Write a Python NumPy: Select indices satisfying multiple conditions in a NumPy array. Before stepping into more programming, let's study some basic stuff but of great importance; 'Boolean'. Just as an integer can take values of -1, 1, 0, etc. and a float can take 0.01, 1.2, etc. A Boolean is something which can either be true or false. Python 2; Python 3

Comparisons, Masks, and Boolean Logic, The array contains 365 values, giving daily rainfall in inches from January 1 to It is also possible to do an element-wise comparison of two arrays, and to� In this article we will discuss how to select elements or indices from a Numpy array based on multiple conditions. Similar to arithmetic operations when we apply any comparison operator to Numpy Array, then it will be applied to each element in the array and a new bool Numpy Array will be created with values True or False.

NumPy where tutorial (With Examples), So what we effectively do is that we pass an array of Boolean values to the So in this case, np.where will return two arrays, the first one carrying the row Note: We'll use Python's datetime module to create date objects. Note: For more information, refer to Decision Making in Python (if , if..else, Nested if, if-elif) Multiple conditions in if statement. Here we’ll study how can we check multiple conditions in a single if statement. This can be done by using ‘and’ or ‘or’ or BOTH in a single statement. Syntax:

NumPy: Count the number of elements satisfying the condition, Posted: 2019-05-29 / Modified: 2019-11-05 / Tags: Python, NumPy The comparison operation of ndarray returns ndarray with bool ( True , False ). In the case of a two-dimensional array, axis=0 gives the count per column, axis=1 gives the� It is called fancy indexing, if arrays are indexed by using boolean or integer arrays (masks). The result will be a copy and not a view. In our next example, we will use the Boolean mask of one array to select the corresponding elements of another array. The new array R contains all the elements of C where the corresponding value of (A<=5) is True.

Comments
  • Try (A<7) & (A>3) (for example).