Numpy Exercise 1

Imports



In [74]:

    
import numpy as np
%matplotlib inline
import matplotlib.pyplot as plt
import seaborn as sns



In [75]:

    
import antipackage
import github.ellisonbg.misc.vizarray as va

Checkerboard

Write a Python function that creates a square (size,size) 2d Numpy array with the values 0.0 and 1.0:

Your function should work for both odd and even size.
The 0,0 element should be 1.0.
The dtype should be float.



In [103]:

    
def checkerboard(size):
    a = np.zeros((size,size), dtype = np.float)
    b = 2
    if size % 2 != 0:
        for element in np.nditer(a, op_flags=['readwrite']):  
            if size % 2 != 0:
                if b % 2 == 0:
                    element[...] = element + 1.0
                    b += 1
                else:
                    b += 1
        return a
    else:
            c = [1,0]
            d = [0,1]
            e = []
            f = size / 2
            g = list(range(1, size + 1))
            for item in g:
                if item % 2 != 0:
                    e.append(c * f)
                else:
                    e.append(d * f)
            h = np.array(e, dtype = np.float)
            return h
    
print checkerboard(4)









    



[[ 1.  0.  1.  0.]
 [ 0.  1.  0.  1.]
 [ 1.  0.  1.  0.]
 [ 0.  1.  0.  1.]]

Use vizarray to visualize a checkerboard of size=20 with a block size of 10px.



In [104]:

    
va.set_block_size(10)
va.vizarray(checkerboard(20))









    Out[104]:



In [105]:

    
assert True

Use vizarray to visualize a checkerboard of size=27 with a block size of 5px.



In [106]:

    
va.set_block_size(5)
va.vizarray(checkerboard(27))









    Out[106]:



In [107]:

    
assert True



In [108]:

    
a = checkerboard(4)
assert a[0,0]==1.0
assert a.sum()==8.0
assert a.dtype==np.dtype(float)
assert np.all(a[0,0:5:2]==1.0)
assert np.all(a[1,0:5:2]==0.0)

b = checkerboard(5)
assert b[0,0]==1.0
assert b.sum()==13.0
assert np.all(b.ravel()[0:26:2]==1.0)
assert np.all(b.ravel()[1:25:2]==0.0)