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@section('title')
    Introduction to Plotting 
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@section('content')
#    Part 1: Introduction to Plotting 
##Plotting with `matplotlib`
In CS111, we will use Python’s matplotlib library to make plots/graphs/charts. 

Reference materials:
* [CS111 data visualization slides](/content/lectures/datavisualization/data_visualization_slides.pdf)
* [matplotlib examples](http://matplotlib.org/examples)
* [pyplot documentation](http://matplotlib.org/api/pyplot_summary.html)

We'll need to import these modules whenever we want to plot:
```py
import matplotlib.pyplot as plt
import numpy as np
```

# Line plots
```py
plt.figure(figsize=(3,3))
plt.plot([10, 20, 15])
plt.show()
```
Draw the plot here:
<img src='blank.png' style='max-width:200px'>

Note: `plot` allows you to specify the following:
* `color = 'r'`
* `linestyle = 'dashed'`
* `linewidth = 5`


```py
plt.figure(figsize=(3, 3))
plt.plot([1, 3, 5, 7, 9], [5, 1, 3, 1, 5], color='r', linewidth=4)
plt.show()
```
Draw the plot here:
<img src='blankw.png' style='max-width:200px'>

## Controlling axes with axis/xlim/ylim
```py
x = [1, 3, 5, 7, 9]
y = [5, 1, 3, 1, 5]
plt.figure(figsize=(3, 3))
plt.plot(x, y, 'r-.', lw=5) # shortcut for red dash-dot line, linewidth 5
plt.axis([0, 10, 0, 6]) # list with xmin, xmax, ymin, ymax
plt.show()
```
<!-- <img src='redw.png' style='max-width:200px'> -->
<img src='worksheet4.png' style='max-width:200px'> 

```py
x = [1, 3, 5, 7, 9]
y = [5, 1, 3, 1, 5]
plt.figure(figsize=(3, 3))
plt.plot(x, y, 'c:', lw=3) # cyan dotted line, linewidth 3
plt.ylim((-10, 10)) # tuple
plt.show()
```
<!--<img src='cyanw.png' style='max-width:200px'>-->
<img src='worksheet3.png' style='max-width:200px'>

## Adding descriptive text to plot (title, axis & tick labels)

```py
plt.figure(figsize=(4.5, 4.5))

plt.plot(x, y, 'b-.', lw=5)
plt.axis([0, 10, 0, 6])
plt.xticks([1, 5, 9], 
           ['x:p1', 'x:p3', 'x:p5'])
plt.yticks([5, 3, 1], 
           ['y:p1,p5', 'y:pt3', 'y:p2,p4'],
           rotation=90)
plt.xlabel("width for letter W")
plt.ylabel("height for letter W")
plt.title("W is for Wellesley", fontsize=14)
plt.show()
```

### Pre-defined style sheets
Examples in our slide reference use `ggplot`. 
```py
plt.style.use('ggplot')
```
Interested in other style sheets? Here is a [visual matplotlib style sheet reference](https://tonysyu.github.io/raw_content/matplotlib-style-gallery/gallery.html).

<table border=1 padding=5>
<tr><td> No style sheet </td><td> ggplot stylesheet</td></tr>
<tr>
<td>
<img src='nostyleW.png' style='max-width:300px'> 
</td>
<td>
<img src='ggplotw.png' style='max-width:300px'>
</td>
</tr>
</table>

@include('/labs/lab15/_toc')

@stop