COMP1007 Assignment 3 Solved

Requirements: 

•              Please submit a single Python source file that contains all your solutions.

•              Use comments to label the question ID (i.e., Question 1, Question 2, etc.)

•              For each Python function, you need to provide some testing statements to test your function. 

[10 marks per question]

1.              Write a Python function to count the number of characters in a string, and return a dictionary. E.g., if the input to the function is "google.com", the returned dictionary should be: {'g': 2, 'o': 3, 'l': 1, 'e': 1, '.': 1, 'c': 1, 'm': 1}.

 

2.              Write a Python function to check if a string contains all letters of the alphabet (case insensitive). For example, if the input string is "The quick brown fox jumps over the lazy cat", the function should return True; if the input string is "abcdefghijklmnopqrstuvwxy", the function should return False.

 

3.              Write a Python function that takes a string as input and returns a new string by removing duplicate characters of the input string. E.g., if the input string is "Hello“, the output string should be "Helo"; if the input string is "Google", the output string should be "Gole". 

 

4.              Write a Python function that takes two parameters, a string str and a positive integer n. The function returns a new string which lowercases the first n characters of the input string str. For example, if str is "United States" and n is 5, the returned string should be "united States"; if str is "United States" and n is 8, the returned string should be "united states".

 

5.              Write a Python function that counts the vowels of a given string. Vowels include 'a', 'e', 'i', 'o', 'u' and their uppercases. E.g., if the string is "Internet", the function should return 3.

 

6.              Write a NumPy program to create an array of all the even integers from 100 to 200. Output the length of your array which should be 51.

 

7.              Write a NumPy program to create an array of 100 ones followed by 100 fives, and then followed by 100 tens. Please use numpy.ones(), numpy.full(), and numpy.concatenate(). 

[Self-learning]: Please learn the usage of numpy.concatenate() from https://docs.scipy.org/doc/numpy/reference/generated/numpy.concatenate.html 

8.              Write a NumPy function to add a vector to each row of a given matrix. Assume the vector has the same dimension as the row of the given matrix. For example, if the vector is [2, 3, 4] and the given

matrix is [8      9          10], then the matrix should be changed to         [10      12            14].

               5      6       7                                                                                               7         9       11

 

9.              Given a NumPy array that stores a vector of Centigrade values. Write a NumPy function to convert the values of Centigrade degrees into Fahrenheit degrees. 

[Remark: find the conversion formula by yourself through Internet.]

 

10.           Write a NumPy program that generates ten 100x100 arrays whose data follows standard normal distribution. Then output the min, max, mean, and standard deviation of the data for each array. Next, sum up the ten 100x100 arrays into a single 100x100 array. Output the min, max, mean, and standard deviation of this new array.

[Remark: this question helps you understand the sum of normally distributed random variables. For students who are interested in statistics, please check

https://en.wikipedia.org/wiki/Sum_of_normally_distributed_random_variables ]