Lab activity

The purpose of the lab is to practice and measure one’s preparation: the exercises are not too difficult, if you have followed the lectures. However, no score is put on them.

Working mode: students should work independently or in small groups, without disturbing colleagues. Group work is fruitful only if everyone participates and if everyone writes their own solution for all exercises.

The teacher will try as much as possible not to occupy the time of the laboratory to introduce new material, although sometimes this will be necessary. The lecturer is available to help students, who can start working even before the lecturer arrives in the classroom, if they wish.

Recommendations: Read the text of the exercises carefully before ask for clarification. In any case, I will be in the classroom with you.

Using test files: To help you complete this exercise you have test programs available to test your solution. These are similar to those you will have on the exam, so I recommend that you learn how to use them. To complete the exercise you will need to

• write a solution file with the specified name;
• have inside the function with the specified name;
• place the corresponding test file in the same folder;
• run the python3 <fileditest> command in that folder;

where <fileditest> should obviously be replaced by the name of the test appropriate for the exercise you are working on. For each exercise there is an independent test file, so that you can easily work on the exercises one at a time.

The result of each test is a screen(s) in which it is shown:

• whether the file with the correct name was found,
• whether the file contains the function with the correct name,
• whether calls to the function with different parameter values return correct results.

For each function written, calls are made with different values of the parameters. The outcome of the tests is reported with the character

• E if the call cannot be executed,
• F if the function does not return the correct result,
• . if the function returns the correct result.

Sum elements of a numeric matrix

Write a function mat_sum(m) that:

• takes as argument a matrix m, represented as a list of lists;
• returns the sum of all elements in m.

We represent an r × c matrix in Python as a list with length r, where each element is a list of length c. You may assume that the argument is well formed, with r ≥ 1, c ≥ 1, and all the lists representing rows contain c numeric elements.

Python code must be saved in file: mat_sum.py

Test file (download by right click): test_mat_sum.py

Minimum element in a numeric matrix

Write a function mat_min(m) that:

• takes as argument a matrix m, represented as a list of lists;
• returns the value of the minimum element in m.

We represent an r × c matrix in Python as a list with length r, where each element is a list of length c. You may assume that the argument is well formed, with r ≥ 1, c ≥ 1, and all the lists representing rows contain c numeric elements.

Python code must be saved in file: mat_min.py

Test file (download by right click): test_mat_min.py

Maximum element position in a numeric matrix

Write a function mat_posmax(m) that:

• takes as argument a matrix m;
• returns a pair of integers, e.g. by a return i, j, that are the row and column indices where the maximum element in the matrix appears. In case of more maxima, the position of the first occurrence must be returned (minimum row index, and in case of more maxima in that row minimum column index)

Python code must be saved in file: mat_posmax.py

Test file (download by right click): test_mat_posmax.py

Sum of elements in the diagonal of a squared numeric matrix

Write a function mat_sumdiagonal(m) that:

• takes as argument a square matrix m, represented as a list of lists;
• returns the sum of elements in the main diagonal of m.

We represent an r × c matrix in Python as a list with length r, where each element is a list of length c. You may assume that the argument is well formed, with r ≥ 1, c = r, and all the lists representing rows contain c numeric elements.

Python code must be saved in file: mat_sumdiagonal.py

Test file (download by right click): test_mat_sumdiagonal.py

Row sums of a numeric matrix

Write a function mat_row_sums(m) that:

• takes as argument a matrix m, represented as a list of lists;
• returns a list in which element i is the sum of all elements in row i of m. The length of the returned list is equal to the number of rows in m.

We represent an r × c matrix in Python as a list with length r, where each element is a list of length c. You may assume that the argument is well formed, with r ≥ 1, c ≥ 1, and all the lists representing rows contain c numeric elements.

Python code must be saved in file: mat_row_sums.py

Test file (download by right click): test_mat_row_sums.py

Column sums of a numeric matrix

Write a function mat_col_sums(m) that:

• takes as argument a matrix m, represented as a list of lists;
• returns a list in which element i is the sum of all elements in column i of m. The length of the returned list is equal to the number of columns in m.

We represent an r × c matrix in Python as a list with length r, where each element is a list of length c. You may assume that the argument is well formed, with r ≥ 1, c ≥ 1, and all the lists representing rows contain c numeric elements.

Python code must be saved in file: mat_col_sums.py

Test file (download by right click): test_mat_col_sums.py

Position of row having maximum sum

Write a function mat_posmaxrow(m) that:

• takes as argument a matrix m, represented as a list of lists;

• returns the position of the row having maximum sum. E.G., if called with argument

  [ [2, 4, 3, 6, 8], [3, 1, 4, 0, 0], [9, 5, 9, 7, 4] ]

  value 2 should be returned, since row 2 has sum 34, while rows in position 0 and 1 have sum 23 and 8 respectively.

We represent an r × c matrix in Python as a list with length r, where each element is a list of length c. You may assume that the argument is well formed, with r ≥ 1, c ≥ 1, and all the lists representing rows contain c numeric elements.

Python code must be saved in file: mat_posmaxrow.py

Test file (download by right click): test_mat_posmaxrow.py