One-dimensional Numpy

Question 1

Creating a numpy array

Answer 1

a = np.array([0,1,2,3,4])

a

Question 2

Changing an element in an array - same as in list

Answer 2

We can change the value of the array, consider the array c:

# Create numpy array
​
c = np.array([20, 1, 2, 3, 4])
c
array([20,  1,  2,  3,  4])
We can change the first element of the array to 100 as follows:

c[0]=100
c

array([100, 1, 2, 3, 4])

Question 3

Slicing an array

Answer 3

d = c[1:4]
d
array([1, 2, 3])

Question 4

Select multiple elements

Answer 4

Similarly, we can use a list to select a specific index. The list ‘ select ‘ contains several values:

0,2,3
# Create the index list
select = [0,2,3]

We can use the list as an argument in the brackets. The output is the elements corresponding to the particular index:

# Use List to select elements
d = c[select]
d

array([100, 2, 300])

Question 5

Number of elements in an array

Answer 5

a.size

Question 6

Number of dimensions in an array

Answer 6

a.ndim

Question 7

Mean of an array

Answer 7

a.mean()

Question 8

Max value

Answer 8

a.max()

Question 9

Min value

Answer 9

a.min()

Question 10

Dot product

Answer 10

np.dot(u, v)

7

Question 11

Add a value to every elements in an array

Answer 11

u + 1

array([2, 3, 4, 0])

Question 12

Linspace fucntion

Answer 12

np.linspace(-2, 2, num=5)

array([-2., -1., 0., 1., 2.])

Question 13

Plot vectors

Answer 13

a = np.array([-1, 1])
b = np.array([1, 1])
Plotvec2(a, b)