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D03 Piscine AI - Data Science
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Introduction
While working on a dataset it is important to check the distribution of the data. Obviously, for most of humans it is difficult to visualize the data in more than 3 dimensions
Viz is important to understand the data and to show results. We have already seen there are some basinc viz functionalities in Pandas. Now we'll discover two of the most know viz libraries in Python:
- Pandas viz
- Matplotlib
- Plotly
Pandas viz is pratique: rapid plot, relies on Matplotlib. (check matplotlib doc sometimes not all params are detailed in pandas doc) For more elaborate plots Matplotlib is necessary
And finaly Plotly is a interactive plot library.s
Rules
Always a title, legend, ...s
Ressources
s https://matplotlib.org/3.3.3/tutorials/index.html https://towardsdatascience.com/matplotlib-tutorial-learn-basics-of-pythons-powerful-plotting-library-b5d1b8f67596
https://github.com/rougier/matplotlib-tutorial https://jakevdp.github.io/PythonDataScienceHandbook/05.13-kernel-density-estimation.html
Exercise 1 Pandas plot 1
The goal of this exercise is to learn to create plots with use Pandas. Panda's .plot()
is a wrapper for matplotlib.pyplot.plot()
.
Here is the data we will be using:
df = pd.DataFrame({
'name':['christopher','marion','maria','mia','clement','randy','remi'],
'age':[70,30,22,19,45,33,20],
'gender':['M','F','F','F','M','M','M'],
'state':['california','dc','california','dc','california','new york','porto'],
'num_children':[2,0,0,3,8,1,4],
'num_pets':[5,1,0,5,2,2,3]
})
- Reproduce this plot. This plot is called a bar plot
The plot has to contain:
- the title
- name on x-axis
- legend
Correction
- This question is validated if the plot reproduces the plot in the image. It has to contain a title, an x-axis name and a legend.
Exercise 2: Pandas plot 2
The goal of this exercise is to learn to create plots with use Pandas. Panda's .plot()
is a wrapper for matplotlib.pyplot.plot()
.
df = pd.DataFrame({
'name':['christopher','marion','maria','mia','clement','randy','remi'],
'age':[70,30,22,19,45,33,20],
'gender':['M','F','F','F','M','M','M'],
'state':['california','dc','california','dc','california','new york','porto'],
'num_children':[4,2,1,0,3,1,0],
'num_pets':[5,1,0,2,2,2,3]
})
- Reproduce this plot. This plot is called a scatter plot. Do you observe a relationship between the age and the number of children ?
The plot has to contain:
- the title
- name on x-axis
- name on y-axis
Correction
- This question is validated if the plot reproduces the plot in the image. It has to contain a title, an x-axis name and an y-axis name. You should also observe that the older people are, the the more children they have.
Exercise 3 Matplotlib 1
The goal of this plot is to learn to use Matplotlib to plot data. As you know, Matplotlib is the underlying library used by Pandas. It provides more options to plot custom visualizations. Howerver, most of the plots we will create with Matplotlib can be reproduced with Pandas' .plot()
.
- Reproduce this plot. We assume the data points have integers coordinates.
The plot has to contain:
- the title
- name on x-axis and y-axis
- x-axis and y-axis are limited to [1,8]
- style:
- red dashdot line with a width of 3
- blue circles with a size of 12
Correction
- This question is validated if the plot reproduces the plot in the image and respect those criteria
- the title
- name on x-axis and y-axis
- x-axis and y-axis are limited to [1,8]
- style:
- red dashdot line with a width of 3
- blue circles with a size of 12
Exercise 4 Matplotlib 2
The goal of this plot is to learn to use Matplotlib to plot different lines in the same plot on different axis using twinx
. This very useful to compare variables in different ranges.
Here is the data:
left_data = [5, 7, 11, 13, 17]
right_data = [0.1, 0.2, 0.4, 0.8, -1.6]
x_axis = [0.0, 1.0, 2.0, 3.0, 4.0]
- Reproduce this plot
The plot has to contain:
- the title
- name on left y-axis and right y-axis
- style:
- left data in black
- right data in red
Correction
- This question is validated if the plot reproduces the plot in the image and respect those criteria
The plot has to contain:
- the title
- name on left y-axis and right y-axis
- style:
- left data in black
- right data in red
https://matplotlib.org/gallery/api/two_scales.html
Exercise 5 Matplotlib subplots
The goal of this exercise is to learn to use Matplotlib to create subplots.
- Reproduce this plot using a for loop:
The plot has to contain:
-
6 subplots: 2 rows, 3 columns
-
Keep space between plots:
hspace=0.5
andwspace=0.5
-
Each plot contains
- Text (2,3,i) centered at 0.5, 0.5. Hint: check the parameter
ha
oftext
- a title: Title i
- Text (2,3,i) centered at 0.5, 0.5. Hint: check the parameter
Correction
- The question is validated if the plot reproduces the image and the given criteria:
The plot has to contain:
-
6 subplots: 2 rows, 3 columns
-
Keep space between plots:
hspace=0.5
andwspace=0.5
-
Each plot contains
- Text (2,3,i) centered at 0.5, 0.5. Hint: check the parameter
ha
oftext
- a title: Title i
- Text (2,3,i) centered at 0.5, 0.5. Hint: check the parameter
Check that the plot has been created with a for loop.
Exercise 6 Plotly 1
Plotly has evolved a lot in the previous years. It is important to always check the documentation.
Plotly comes with a high level interface: Plotly Express. It helps building some complex plots easily. The lesson won't detail the complex examples. Plotly express is quite interesting while using Pandas Dataframes because there are some built-in functions that leverage Pandas Dataframes.
The plot outputed by Plotly is interactive and can also be dynamic.
The goal of the exercise is to plot the price of a company. Its price is generated below.
returns = np.random.randn(50)
price = 100 + np.cumsum(returns)
dates = pd.date_range(start='2020-09-01', periods=50, freq='B')
df = pd.DataFrame(zip(dates, price),
columns=['Date','Company_A'])
- Using Plotly express, reproduce the plot in the image. As the data is generated randomly I do not expect you to reproduce the same line.
The plot has to contain:
- title
- x-axis name
- yaxis name
- Same question but now using
plotly.graph_objects
. You may need to useinit_notebook_mode
fromplotly.offline
.
https://plotly.com/python/time-series/e
Correction
- This question is validated if the plot is in the image is reproduced using Plotly express given those criteria:
The plot has to contain:
- a title
- x-axis name
- yaxis name
2.This question is validated if the plot is in the image is reproduced using plotly.graph_objects
given those criteria:
The plot has to contain:
- a title
- x-axis name
- yaxis name
Exercise 7 Plotly Box plots
The goal of this exercise is to learn to use Plotly to plot Box Plots. It is t is a method for graphically depicting groups of numerical data through their quartiles and values as min, max. It allows to compare quickly some variables.
Let us generate 3 random arrays from a normal distribution. And for each array add respectively 1, 2 to the normal distribution.
y0 = np.random.randn(50)
y1 = np.random.randn(50) + 1 # shift mean
y2 = np.random.randn(50) + 2
- Plot in the same Figure 2 box plots as shown in the image. In this exercise the style is not important.
The plot has to contain:
- the title
- the legend
https://plotly.com/python/box-plots/
Correction
- This question is validated if the plot is in the image is reproduced given those criteria:
The plot has to contain:
- the title
- the legend
import plotly.graph_objects as go
import numpy as np
y0 = np.random.randn(50)
y1 = np.random.randn(50) + 1 # shift mean
y2 = np.random.randn(50) + 2
fig = go.Figure()
fig.add_trace(go.Box(y=y0, name='Sample A',
marker_color = 'indianred'))
fig.add_trace(go.Box(y=y1, name = 'Sample B',
marker_color = 'lightseagreen'))
fig.show()