Course Content

# Ultimate Visualization with Python

1. Matplotlib Introduction

2. Creating Commonly Used Plots

4. More Statistical 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

1. Use the correct function for creating a line plot.
2. Pass in the correct order `x_data` (x-axis) and `y_data` (y-axis) as the first two arguments.
3. Pass the rightmost argument such that the plot will have `'o'` markers and dashed lines.

Everything was clear?

Section 2. Chapter 1