Course Content

# Ultimate Visualization with Python

1. Matplotlib Introduction

2. Creating Commonly Used Plots

5. Plotting with Seaborn

Ultimate Visualization with Python

## Line Plot

Congratulations on completing the first section! Since you have already created a plot with a single point on it, it's time to create a line plot.

### Applications

**Line plot** is used to depict the relationship between two variables (e.g. x, y) using straight lines. More formally, it shows the relationship between **continuous** or **ordinal** variables in a continuous data point manner. Moreover, it can show how a certain variable changes with time.

### Creating a Line Plot

We'll use a function from `pyplot`

that we're already familiar with to create line plots: `plot()`

. Let’s have a look at an example of a line plot which shows a quadratic relationship between two variables:

## Code Description

`import matplotlib.pyplot as plt`

import numpy as np

First, we import

`pyplot`

with `plt`

alias and `numpy`

with `np`

alias.
`data_linear = np.arange(0, 6)`

Then comes a more interesting part where we create a

`numpy`

array with numbers from 0 to 5 inclusive using `np.arange()`

function.
`data_squared = data_linear ** 2`

Next, using

`numpy`

broadcasting (vectorization), we square every element of the previously created `data_linear`

array.
`plt.plot(data_linear, data_squared, '-o')`

To create a line plot, we use

`data_linear`

for x-values and `data_squared`

for y-values. We format the plot with `'-o'`

, where '-' signifies solid lines ('-' is the default value) and 'o' represents markers. `'--o'`

, for example, will create dashed lines with markers.
`plt.show()`

Finally, we display the line plot.

In fact, this code can even be further simplified. Have a look at another example:

Here we only used one array `data_squared`

for plotting. But how does `matplotlib`

understand which values are used for x-axis and y-axis?

Note

If only one array (pandas

`Series`

object) is specified, its indices will be used for x-axis and values for y-axis.

The indices in this example are numbers from `0`

to `5`

including (just integer indices of a usual array of size `6`

).

# Task

- Use the correct function for creating a line plot.
- Pass in the correct order
`x_data`

(x-axis) and`y_data`

(y-axis) as the first two arguments. - Pass the rightmost argument such that the plot will have
`'o'`

markers and dashed lines.

Everything was clear?