NumPy for ML: Tutorial 3

NumPy Tutorial 3

Concept: Targeting Data (Indexing)

In Python, to get a number from a matrix, you use two sets of brackets [row][col]. In NumPy, we use a cleaner, comma-separated syntax.

Python List
val = list[0][1]
Two steps (slow)

NumPy Array
val = arr[0, 1]
One step (fast)

Activity: Target the Number

We want to extract the number 60 from this matrix. Drag the correct Row Index and Column Index into the code below.

Remember: Computer Science counting starts at 0.

Columns: 0 1 2

Row 0 Row 1

Code Builder:

                    number = arr[
                    Row
 , 
                    Col

                    ]
                

Draggable Indices:

Knowledge Check

Which syntax is valid for selecting the first element (top-left) in a NumPy matrix?

A. array(0, 0)

B. array[0, 0]

C. array[1, 1]