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Python: Numpay – P2



Learning : Python Numpy – P2
Subject: Two Dimensional array and some basic commands

In real mathematics word we mostly using arrays with more than one dimensions, for example with two dimension array we can store a data as

So let’s start, if we want to create an array with 24 number in it starting from 0 to 23 we use the command np.range. as bellow :

 # We are using np.range to create an array of numbers between (0-23) 

m_array = np.arange(24)
print(m_array)
[Output]: 
[ 0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23]
 


And if we want the array to be in a range with certain incriminating amount we may use this command:

 # Create array between 2-3 with 0.1 interval 

m_array = np.arange(2, 3, 0.1)
print(m_array)
[Output]: 
[ 2. , 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9]


Now if we want to create an array say 3×3 fill with random numbers from (0-10) we use random function in numpy as bellow:

 # create 3x3 Array with random numbers 0-10 
m_array = np.random.randint(10, size=(3,3))
print(m_array)
[Output]: 
[[6 0 7]
 [1 9 8]
 [5 8 9]] 



And if we want the random number ranges to be between two numbers we use this command:

# Array 3x3 random values between (10-60)
m_array = np.random.randint(10,60, size=(3,3))
[Output]: 
[[11 23 50]
 [36 44 18]
 [56 24 30]] 


If we want to reshape the array; say from 4×5 (20 element in the array) we can reshape it but with any 20-element size. Here is the code:

# To crate a randome numbers in an array of 4x5 and numbers range 10-60.
m_array = np.random.randint(10,60, size=(4,5))
print(m_array)

# We will reshape the 4x5 to 2x10
new_shape = m_array.reshape(2,10)
print ('\n   Tne new 2x10 array:\n',new_shape)
[Output]:
[[37 11 56 18 42]
 [17 12 22 16 42]
 [47 29 17 47 35]
 [49 55 43 13 11]]

Tne new 2x10 array:
[[37 11 56 18 42 17 12 22 16 42]
 [47 29 17 47 35 49 55 43 13 11]]


Also we can convert a list to an array,

# Convert a list l=([2,4,6,8]) to a 1D array
# l is a list with [2,4,6,8] values.
l=([2,4,6,8])
print('  l= ',l)
# Convert it to a 1D array.
ar = np.array(l)
print('\n  Type of l:',type(l),', Type of ar:',type(ar))
print('  ar = ',ar)

[Output]:
l=  [2, 4, 6, 8] 
Type of: class'list'  , Type of ar: class 'numpy.ndarray'
ar =  [2 4 6 8]


If we want to add a value to all elements in the array, we just write:

# Adding 9 to each element in the array

 
print('ar:',ar)
ar = ar + 9
print('ar after adding 9:',ar)

[Output]:
ar:  [2 4 6 8]
ar after adding 9: [11 13 15 17]


:: numpy Commands::

Command Comments and Outputs
my_array = np.array([1,2,3,4,5]) Create an array with 1 to 5 integer
len(my_array) Get the array length
np.sum(my_array) get the sum of the elements in the array

my_array = np.array([1,2,3,4,5])
print(np.sum(my_array))
[Output]: 15
np.max(my_array) # Get the maximum number in the array
my_array = np.array([1, 2, 3,4,5])
max_num = np.max(my_array)
[Output]: 5
np.min(my_array) # Get the minimum number in the array
my_array = np.array([1, 2, 3,4,5])
min_num = np.min(my_array)
[Output]: 1
my_array = np.ones(5)
Output: [ 1., 1., 1., 1., 1.]
create array of 1s (of length 5)
np.ones(5)
Output: [ 1., 1., 1., 1., 1.]
m_array = np.arange(24)
print(m_array)
# To create an array with 23 number.
[ 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23]
m_array = np.arange(2, 3, 0.1)
print(m_array)
# Create an array from 2 to 3 with 0.1 interval value increments.
[ 2. , 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9]
m_array = np.random.randint(10, size=(3,3))
print(m_array)
# Create a 3×3 array with random numbers between (0,10)
[[6 0 7]
[1 9 8]
[5 8 9]]
m_array = np.random.randint(10,60, size=(3,3)) # Create a 3×3 array with random numbers between (10,60)
[[11 23 50]
[36 44 18]
[56 24 30]]
# Create a 4×5 array with random numbers.
m_array = np.random.randint(10,60, size=(4,5))

# Reshape m_array from 4×5 to 2×10
new_shape = m_array.reshape(2,10)
print(m_array)
print(new_shape)

# m_array 4×5
[[37 11 56 18 42]
[17 12 22 16 42]
[47 29 17 47 35]
[49 55 43 13 11]]

# Tne new 2×10 array:
[[37 11 56 18 42 17 12 22 16 42]
[47 29 17 47 35 49 55 43 13 11]]

# convert a list to array:
l=[2,4,6,8]
ar = np.array(l)
# check data type for l and ar:
print(‘\n Type of l:’,type(l),’, Type of ar:’,type(ar))
[Output]:
l = [2, 4, 6, 8]
ar = [2, 4, 6, 8]
Type of l: class ‘list,’, Type of ar: class ‘numpy.ndarray’
# Adding 9 to each element in the array
ar = ar + 9
[11 13 15 17]


:: numpy Sessions ::

Sessions 1 Sessions 2 Sessions 3 Sessions 4




:: Some Code output ::

Create array with 24 numbers (0-23).
Reshape array to 4×6.
Create random array of numbers (0-10), size 3×3.
Reshape 4×5 array to 2×10.
Convert list to array.



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  1. November 13, 2019 at 10:47 am
  2. November 13, 2019 at 10:55 am

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