diff -r 88a01948450d -r d33698326409 accessing_parts_of_arrays/questions.rst
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+++ b/accessing_parts_of_arrays/questions.rst	Wed Dec 01 16:51:35 2010 +0530
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+Objective Questions
+-------------------
+
+.. A mininum of 8 questions here (along with answers)
+
+1. Given the array, ``A = array([12, 15, 18, 21])``, how do we access
+   the element ``18``?
+
+   Answer: ``A[2]``
+
+#. Given the array, ``A = array([12, 15, 18, 21])``, what element is
+   accessed by ``A[1]``
+
+   Answer: ``15``  
+
+#. Given the array, ``A = array([12, 15, 18, 21])``, what element is
+   accessed by ``A[-3]``?
+
+   Answer: ``15``  
+
+#. Given the array, ``A = array([12, 15, 18, 21])``, how do you change
+   the element ``15`` to ``51``?
+
+   Answer: ``A[1] = 51``
+
+#. Given the array, ``A = array([12, 15, 18, 21])``, what is ``A``
+   after the execution of the statement ``A[3] = 24``?
+
+   Answer: ``array([12, 15, 18, 24])``
+
+#. Given the array, ``A = array([12, 15, 18, 21])``, what is the
+   result of the statement, ``A[4] = 24``?
+
+   Answer: IndexError: index out of bounds
+
+#. Given the array, ``B = array([[12, 15], [18, 21]])``, how do we
+   access the element ``18``? 
+
+   Answer: ``A[0, 0]``
+
+#. Given the array, ``B = array([[12, 15], [18, 21]])``, what is the
+   result of ``B[1]``? 
+
+   Answer:  ``array([18, 21])``
+
+#. Given the array, ``B = array([[12, 15], [18, 21]])``, what is the
+   result of ``B[1, 1]``?
+
+   Answer:  ``21``
+
+#. Given the array, ``B = array([[12, 15], [18, 21]])``, what element
+   is accessed by ``B[-1, -2]``?
+
+   Answer:  ``18``   
+
+#. Given the array, ``B = array([[12, 15], [18, 21]])``, how do you
+   change the element ``15`` to ``51``?
+
+   Answer:  ``B[0, 1] = 51``   
+
+#. Given the array, ``B = array([[12, 15], [18, 21]])``, what is the
+   value of B, after executing, ``B[0] = 0``?
+
+   Answer:  ``array([[0, 0], [18, 21]])``   
+
+#. Given the array, 
+   
+   ::
+   
+     B = array([[10, 11, 12, 13],
+                [20, 21, 22, 23],
+                [30, 31, 32, 33],
+                [40, 41, 42, 43]])
+
+   Obtain the elements, ``[[21, 22], [32, 32]]``
+
+   Answer:  ``B[1:3, 1:3]``   
+
+#. Given the array, 
+   
+   ::
+   
+     B = array([[10, 11, 12, 13],
+                [20, 21, 22, 23],
+                [30, 31, 32, 33],
+                [40, 41, 42, 43]])
+
+   Obtain the elements, ``[[10, 13], [30, 33]]``
+
+   Answer:  ``B[::2, ::3]``
+
+#. What command is used to read an image file?
+
+   a. imshow
+   #. imread
+   #. imopen
+   #. open
+
+   Answer: ``imread``   
+
+#. If ``P`` is ``array([12, 13, 14, 15])`` then ``P.shape`` gives
+   ``(4, 1)``. True or False?
+
+   Answer: False
+     
+Larger Questions
+----------------
+
+.. A minimum of 2 questions here (along with answers)
+
+1. Given the array, 
+   ::
+   
+     B = array([[10, 11, 12, 13],
+                [20, 21, 22, 23],
+                [30, 31, 32, 33],
+                [40, 41, 42, 43]])
+
+   Change the array to 
+   ::
+   
+     B = array([[10, 11, 10, 11],
+                [20, 21, 20, 21],
+                [10, 11, 10, 11],
+                [20, 21, 20, 21]])
+
+   using slicing and striding. 
+
+   Answer::
+
+     B[:2, 2:] = B[:2, :2]
+     B[2:, :2] = B[:2, :2]
+     B[2:, 2:] = B[:2, :2]
+
+#. Find out how to display a grayscale image with proper colors. Hint,
+   use ``?`` on ``imshow``. 
+   
+   Answer: ``cmap=cm.gray``
+                  
+#. From the image, ``tagore-einstein.png``, 
+   a. show only the face of Einstein. 
+   b. show only the face of Tagore. 
+
+   Hint, use ``imread`` to read the image and ``imshow`` to show the
+   image.  Use ``cm.gray`` as ``cmap`` to display the image properly.   
+
+   Answer:: 
+
+     F = imread('tagore-einstein.png')
+     imshow(F[:210, 20:180], cmap=cm.gray)
+
+     F = imread('tagore-einstein.png')
+     imshow(F[30:300, 320:480], cmap=cm.gray)
+
+.. #[Puneeth: This question contains answer to previous
+.. question. Shouldn't be shown at the same time.]
+
+
+