Programming Python for Business Analytics Week 3

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Questions and Answers

Which library is primarily used for numerical analysis in Python?

NumPy (correct)
Scikit-learn
Pandas
Matplotlib

NumPy allows for efficient computations with large multi-dimensional arrays.

True (A)

What is the time taken by np.sum() to sum 10 million numbers?

0.0009 seconds

Scikit-learn is built on top of ___.

NumPy Signup and view all the answers

Match the following Python libraries with their primary functions:

NumPy = Numerical analysis Pandas = Data manipulation and analysis Matplotlib = Data visualization Scikit-learn = Machine learning Signup and view all the answers

What is a key feature of NumPy?

Fast computation of large multi-dimensional arrays (B) Signup and view all the answers

What Python shortcut is used for importing the NumPy library?

np Signup and view all the answers

What method is used to calculate the total in the provided code snippet?

np.sum() (D) Signup and view all the answers

Broadcasting in NumPy allows operations between arrays of different shapes without any issues.

False (B) Signup and view all the answers

Name one mathematical operation that is considered an aggregation.

sum Signup and view all the answers

The result of multiplying array `X` by array `a` is ____, where `X` is `np.array([[1,2,3],[4,5,6]])` and `a` is `np.array([0,1,0])`.

array([[0, 2, 0], [0, 5, 0]]) Signup and view all the answers

Match the following aggregation functions with their description:

sum = Calculates the total of elements max = Finds the maximum value mean = Calculates the average of elements min = Finds the minimum value Signup and view all the answers

What error occurs when trying to add two arrays of differing shapes without appropriate reshaping?

ValueError (A) Signup and view all the answers

The output of reshaping an array to (2,2) with elements [0, 10, 20, 30] will be an array containing two rows and two columns.

True (A) Signup and view all the answers

What is the result of the operation x.reshape((4,1)) when x = np.array([0,10,20,30])?

array([[ 0], [10], [20], [30]]) Signup and view all the answers

The total of outer product can be calculated using the formula: total = σ_{i=1}^{n} x_i ⋅ σ_{j=1}^{m} y_j or using _____ instead of for-loops.

vectorization Signup and view all the answers

Match the following operations with their result:

x + y = ValueError due to shape mismatch x.reshape((4, 1)) = Array with shape (4, 1) x.reshape((2, 2)) = Array with shape (2, 2) x + y.reshape((1, 3)) = Properly broadcasted operation Signup and view all the answers

What does the expression A[0, :] return?

The first row of matrix A (D) Signup and view all the answers

A slicing operation of the form A[0:2] returns the first two elements of a matrix.

True (A) Signup and view all the answers

What is the output of the expression x[:, 1] when x is defined as np.array([[3,2,1], [4,5,6]])?

[2, 5] Signup and view all the answers

The expression x[x > 2] extracts elements from the array x that are greater than ___ .

2 Signup and view all the answers

Match the following expressions with their corresponding outputs:

A[0:2, 1:3] = (2,2) A[:2, 1:] = (2,2) x[-1, :] = (3,) x[:2, 1:2] = (2,1) Signup and view all the answers

What is the output of the expression x[::-1, [2,1,0]] for the array x defined as np.array([[6,5,4], [1,2,3]])?

[[6, 5, 4], [1, 2, 3]] (A) Signup and view all the answers

Boolean indexing works with both NumPy arrays and regular Python lists.

False (B) Signup and view all the answers

What shape does the expression A[:, :2] return when A is defined as np.array([[0,1,2], [3,4,5]])?

(2,2) Signup and view all the answers

What function is used to sort an array in ascending order?

np.sort(array) (D) Signup and view all the answers

The command np.sort(-a) sorts an array in ascending order.

False (B) Signup and view all the answers

What value of x produces the minimum of cos(x) between [0, 6]?

3.1415926999999 Signup and view all the answers

The function used to generate random numbers uniformly is np.random.______

rand Signup and view all the answers

Match the following NumPy functions with their description:

np.random.seed(N) = Sets the seed for random number generation np.argmax(array) = Returns the index of the maximum value in the array np.argmin(array) = Returns the index of the minimum value in the array np.random.permutation(array) = Randomly permutes the elements of an array Signup and view all the answers

Which of the following statements about direct sorting is correct?

np.sort(array, axis=None) sorts the entire array. (D) Signup and view all the answers

Np.random.rand(N) and np.random.randn(N) produce the same type of random numbers.

False (B) Signup and view all the answers

To find the maximum value in an array, you would use the function np.max(______).

array Signup and view all the answers

What does `A[A > 2]` return when A is defined as `np.array([[0,3,1], [4,2,5]])`?

[3, 4, 5] (D) Signup and view all the answers

Creating a slice of a NumPy array results in a copy of the original array.

False (B) Signup and view all the answers

What operation does `A * 2` perform on the NumPy array?

It multiplies each element of A by 2. Signup and view all the answers

In NumPy, `A.copy()` creates a __________ of the array A.

copy Signup and view all the answers

Match the following functions with their descriptions:

np.sum() = Calculates the sum of array elements. np.dot() = Performs matrix product. A.copy() = Creates a separate copy of the array. A[A > 2] = Returns elements that are greater than 2. Signup and view all the answers

What will happen if you execute `B[0, 0] = 10` after creating B via `B = A.copy()`?

B[0, 0] will change to 10, but A[0, 0] remains unchanged. (A) Signup and view all the answers

Element-wise operations like `A + B` perform matrix multiplication in NumPy.

False (B) Signup and view all the answers

In the given context, how are gains calculated when $X_{tj} > 0$?

Gains are calculated as the sum of $X_{tj}$ for each department j for all time periods t where $X_{tj}$ is greater than 0. Signup and view all the answers

Flashcards

NumPy

A Python library for numerical computation, particularly useful for working with vectors and matrices.

Vectors and matrices

Multi-dimensional arrays used for numerical data in Python, efficiently handled by NumPy.

Broadcasting

NumPy's ability to perform operations on arrays of different shapes, automatically expanding smaller arrays to match larger ones.