Question

1. Consider the matrix list x = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]. Write a list comprehension to extract the first column of the matrix [1, 4, 7]. Write another list comprehension to create a vector of twice the square of the middle column.

Answer 1

Hello,

let me write the function definition for the first part of your problem, which says "Write a list comprehension to extract the first column of the matrix".(Since you didn't specified any language so providing the code in python language,)

code starts here:-

def first_column(l):
    column=[]
    for i in l:
        column.append(i[0])
    return column

code ends here:-

the above defined function takes a matrix list as a parameter and then returns the list of all elements present in the first column of matrix.

if the function is called as

print(first_column([[1, 2, 3], [4, 5, 6], [7, 8, 9]]))

then it will produce output as :-

let me show the snapshot of code:-(with the calling of the function)

let us move to the second part of the problem which states that "Write another list comprehension to create a vector of twice the square of the middle column."

let us write function for that:-

code starts here:-

def problem2(l):
    column=[]
    for i in l:
        column.append(i[1]*i[1]*2)
    return column

code ends here:-

when above function is called with the given list as a parameter as :-

print(problem2([[1, 2, 3], [4, 5, 6], [7, 8, 9]]))

then it gives the output as:-

let me show the snapshot of the code with calling the function with given list:-

i hope i was able to solve your problem to a greater extent, please feel free to comment your queries, i will surely respond to them. Please consider my efforts and please upvote my solution.

Thanku:)