diff -r e675f9208b91 -r 4054b1a6392d getting-started-with-arrays/questions.rst --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/getting-started-with-arrays/questions.rst Wed Oct 13 17:32:59 2010 +0530 @@ -0,0 +1,132 @@ +Objective Questions +------------------- + +.. A mininum of 8 questions here (along with answers) + +1. An array in Python is the same as a Python list + + a. True + #. False + +Answer: False + +2. ``x = array([1, 2, 3], [5, 6, 7])`` is a valid statement + + a. True + #. False + +Answer: False + +3. What will be the output of the following code, + :: + + x = array([[1, 2, 3], ['a', 2, 'c']]) + print x[0][0] + x[0][1] + x[0][2] + + a. 6 + #. 123 + #. a2c + #. Error as array takes only homogeneous elements + +Answer: 123 + +4. What will be the output of the following code, + :: + + x = [[1, 2, 3], [4.1, 4.2, 4.3], ['6','7',8]] + y = array(x) + print y[-1][-2] + y[-1][-1] + y[-2][0] + y[0][-2] + + a. 21.1 + #. 12.5 + #. 784.12 + #. Error as array takes only homogeneous elements + + .. 4.2 4.3 2 2 + +Answer: 784.12 + +5. What is the output of the following code, + :: + + x = array([[1, 2, 3], ['a', 2, 'c']]) + identity(x.shape) + + a. Will create an identity matrix of shape (2, 3). + #. ``identity()`` function takes an integer as argument and a tuple + is passed. + #. Will return, array([[1,0,1],[0,1,0]]) + #. Will return, array([[0,1,0],[0,1,0]]) + +Answer: ``identity()`` function takes an integer as argument and a + tuple is passed. + +6. ``ones_like()`` function? + + (A) Returns an array of ones with the same shape and type as a + given array. + (B) Return a new array of given shape and type, filled with ones. + + Read the statements and answer, + + a. Only statement A is correct. + #. Only statement B is correct. + #. Both statement A and B are correct. + #. Both statement A and B are incorrect. + +Answer: Only statement A is correct. + +7. ``zeros_like()`` function? + + (A) Return a new array of given shape and type, filled with zeros. + (B) Returns an array of zeros with the same shape and type as a + given array. + + + Read the statements and answer, + + a. Only statement A is correct. + #. Only statement B is correct. + #. Both statement A and B are correct. + #. Both statement A and B are incorrect. + +Answer: Only statement B is correct. + +8. What will be output of the following code snippet. + :: + + x = linspace(1,10,10).reshape(5,2) + print (x[-3]+x[-4]).sum() + + a. 10.0 + #. 18.0 + #. 14.0 + #. 16.44 + #. Error + +Answer: 18 + +Larger Questions +---------------- + +.. A minimum of 2 questions here (along with answers) + +1. Write a python script to create a 15x15 array of equally spaced 225 + elements from 1 to 1000, add 5 to each of the diagonal elements and + find the sum of all odd rows of the array. Say for example the + array, + :: + + x = array([[1, 2, 3], + [4, 5, 6], + [7, 8, 9]]) + + will give answer 40 ((1+5) + 2 + 3 + 7 + 8 + (9+5)). + +2. For any given array([a1, a2, a3, .. , an]) the Vandermonde matrix + will be [[1, a1, a1**2, .. , a1**(n-1)], [1, a2, a2**2, .. , + a2**(n-1)], .. , [1, an, an**2, .. ,an**(n-1)]]. Write a python + script to generate the Vandermonde matrix and find the determinant + of the matrix for [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, + 16, 17, 18, 19, 20]. [Hint: to find the determinant use the + function ``det()`` from ``linalg`` module.]