Basic Indexing
Every NumPy array has elements and their respective indices. Here we will focus on indices in 1D arrays. Let's take a look at the following image:
Here we have an array of five elements: [9, 6, 4, 8, 10]
. Every element has a positive and negative index. For example, 9
has 0
as its positive index and -5
as its negative index. As you can see, positive indexing in arrays starts at 0
and goes up to n-1
, where n
is the length of the array. Negative indexing, on the other hand, starts at -n
and goes up to -1
.
Accessing Elements by Indices
To access an element by its index, you should specify the index of this element in square brackets, e.g., array[2]
.
Note
If a specified index is out of bounds, an
IndexError
is thrown, so be cautious of that.
Let's take a look at an example:
As you can see, there is nothing complicated here.
Note
It is common practice to access the first element of the array using a positive index (
0
) and the last element using a negative index (-1
).
Since the elements of our array are just numbers, we can perform all kinds of operations on them that we would do with regular numbers:
Here, we calculated the average of the first and the last elements of our array.
Tarea
Calculate the average of the first, fourth, and last elements:
- Use a positive index to access the first element.
- Use a positive index to access the fourth element.
- Use a negative index to access the last element.
- Calculate the average of these numbers.
¿Todo estuvo claro?
Contenido del Curso
Ultimate NumPy
3. Commonly used NumPy Functions
Ultimate NumPy
Basic Indexing
Every NumPy array has elements and their respective indices. Here we will focus on indices in 1D arrays. Let's take a look at the following image:
Here we have an array of five elements: [9, 6, 4, 8, 10]
. Every element has a positive and negative index. For example, 9
has 0
as its positive index and -5
as its negative index. As you can see, positive indexing in arrays starts at 0
and goes up to n-1
, where n
is the length of the array. Negative indexing, on the other hand, starts at -n
and goes up to -1
.
Accessing Elements by Indices
To access an element by its index, you should specify the index of this element in square brackets, e.g., array[2]
.
Note
If a specified index is out of bounds, an
IndexError
is thrown, so be cautious of that.
Let's take a look at an example:
As you can see, there is nothing complicated here.
Note
It is common practice to access the first element of the array using a positive index (
0
) and the last element using a negative index (-1
).
Since the elements of our array are just numbers, we can perform all kinds of operations on them that we would do with regular numbers:
Here, we calculated the average of the first and the last elements of our array.
Tarea
Calculate the average of the first, fourth, and last elements:
- Use a positive index to access the first element.
- Use a positive index to access the fourth element.
- Use a negative index to access the last element.
- Calculate the average of these numbers.
¿Todo estuvo claro?