The problems in Part A should be done without the use of
loops. They can be done with NumPy functions.
The different questions in this part use the array
defined below.
import numpy as np Load NumPy
arr1 = np.array([[2,5,3,-1,0,1,-6,8,1,-9],[-1,3,4,2,0,1,2,7,8,-1],
[3,0,-2,-2,5,4,8,-1,0,2],[3,3,-3,2,4,5,1,9,8,6],
[1,1,0,2,-3,-2,4,-7,0,-9],[0,1,7,8,-5,-4,0,2,5,-9]])
(a) Extract a submatrix arr1_slice1 from arr1 that consists of
the second and third rows of arr1.
(b) Find a one dimensional array that contains the entries of
arr1 that are less than -5.
(c) Determine the number of entries of arr1 that are greater
than 3
(d) Find the mean of the entries of arr1 that are less than
or equal to -2.
(e) Find the sum of the squares of the even entries of arr1.
(f) Determine the proportion of positive entries of arr1
that are greater than 3.
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Assignment 3, Part B
The problems in Part B should be done without the use of
loops. They can be done with NumPy functions.
Use the code below to define arr2 and arr3
arr2 = np.arange(-20,28,2)
arr2 = arr2.reshape((4,6))
arr3 = np.arange(-20,12)
arr3 = arr3.reshape((8,4))
(a) Extract a submatrix from arr2 of elements that are
in rows 0 and 3 and columns 1 and 4 of arr2, then
determine the mean and standard deviation of
those elements.
(b) Multiply each element of arr2 by 3, then add 1
to each element, then replace the even values
of the resulting matrix with 0.
(c) Extract rows 1 and 6 from arr3, find the transpose
of the resulting matrix.
(d) Replace the odd negative entries of arr3 with zeros,
then determine the means of the rows of the
resulting matrix.
(e) Find all entries that are in both arr2 and arr3.
(f) Find all entries that are in arr3 but not arr2.
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Assignment 3, Part C
C1. Suppose that course grades are assigned based on
course average as follows: 90's = A, 80's = B,
70's = C, 60's = D, Below 60 = F.
(i) Define a function called "grade" that takes a course
average as input and returns a grade.
(ii) Use a for loop to take the list of course averages
defined below and convert it into a list of
corresponding course grades.
[99, 73, 60, 91, 93, 92, 68, 55, 60, 79, 79, 92, 51, 78, 68, 90, 99,
62, 58, 76, 78, 65, 92, 83, 95, 82, 92, 85, 83, 65, 85, 61, 69, 72,
63, 79, 59, 63, 85, 97]
