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other:python:matplotlib_by_jyp [2020/02/11 10:25] jypeter [Working with matplotlib (JYP version)] |
other:python:matplotlib_by_jyp [2020/02/11 12:55] jypeter [Starting (and more) with matplotlib] |
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There are lots of online tutorials that often don't show much more than a simple scatter plot with basic page setup. | There are lots of online tutorials that often don't show much more than a simple scatter plot with basic page setup. | ||
- | This page will hopefully give you some keeys to become (progressively) a matplotlib power user. | + | This page will hopefully give you some keys to become (progressively) a matplotlib power user. |
<wrap hi>A good way to start with matplotlib</wrap> is to quickly read this section, practice, and read this section again (and again) | <wrap hi>A good way to start with matplotlib</wrap> is to quickly read this section, practice, and read this section again (and again) | ||
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* later, you may need other matplotlib related modules, for advanced usage | * later, you may need other matplotlib related modules, for advanced usage | ||
- You need to know some **matplotlib specific vocabulary**: | - You need to know some **matplotlib specific vocabulary**: | ||
- | * a Matplotlib **//Figure//** (or //canvas//) is a **graphical window** in which you create your plots... | + | * a Matplotlib **//Figure//** (or //canvas//) is a **graphical window** or //page// in which you create your plots... |
* example: ''my_page = plt.figure()'' | * example: ''my_page = plt.figure()'' | ||
* if you need several display windows at the same time, create several figures!\\ <code>win_1 = plt.figure() | * if you need several display windows at the same time, create several figures!\\ <code>win_1 = plt.figure() | ||
win_2 = plt.figure()</code> | win_2 = plt.figure()</code> | ||
- | * the [[http://matplotlib.org/faq/usage_faq.html#parts-of-a-figure|parts of a figure]] are often positioned in //normalized coordinates//: ''(0, 0)'' is the bottom left of the figure, and ''(1, 1)'' the top right | + | * the [[http://matplotlib.org/faq/usage_faq.html#parts-of-a-figure|parts of a figure]] are usually positioned in //normalized coordinates//: ''(0, 0)'' is the bottom left of the figure, and ''(1, 1)'' is the top right |
* You don't really specify the **page orientation** (//portrait// or //landscape//) of a plot. If you want a portrait plot, it's up to you to create a plot that will look higher than it is large. The idea is not to worry about this and just check the final resulting plot: create a plot, save it, display the resulting png/pdf and then adjust the creation script | * You don't really specify the **page orientation** (//portrait// or //landscape//) of a plot. If you want a portrait plot, it's up to you to create a plot that will look higher than it is large. The idea is not to worry about this and just check the final resulting plot: create a plot, save it, display the resulting png/pdf and then adjust the creation script | ||
* If you do have an idea of the layout of what you want to plot, it may be easier to explicitly specify the figure size/ratio at creation time, and then try to //fill// the normalized coordinates space of the figure | * If you do have an idea of the layout of what you want to plot, it may be easier to explicitly specify the figure size/ratio at creation time, and then try to //fill// the normalized coordinates space of the figure | ||
* ''my_page = plt.figure()'': the ratio of the default figure is ''landscape'', because it is 33% larger than it is high. Creating a default figure will be OK most of the time! | * ''my_page = plt.figure()'': the ratio of the default figure is ''landscape'', because it is 33% larger than it is high. Creating a default figure will be OK most of the time! | ||
- | * ''my_page = plt.figure(figsize=(width, height))'': create a figure with a custom ratio (sizes are considered to be in inches) | + | * ''my_page = plt.figure(figsize=(width, height))'': create a figure with a custom ratio |
- | * ''my_page = plt.figure(figsize=(8.3, 11.7))'': create a figure that will theoretically fill an A4 size page in portrait mode (check [[https://www.papersizes.org/a-paper-sizes.htm|Dimensions Of A Series Paper Sizes]] if you need more size details) | + | * The specified ''width'' and ''height'' are supposed to be in inches (1 inch = 2.54 cm) |
+ | * ''my_page = plt.figure(figsize=(8.3, 11.7))'': create a figure that will theoretically fill an A4 size page in portrait mode (check [[https://www.papersizes.org/a-paper-sizes.htm|Dimensions Of A Series Paper Sizes]] if you need more details about standard paper sizes) | ||
* a Matplotlib **//Axis//** is a **plot** inside a Figure... [[http://matplotlib.org/faq/usage_faq.html#parts-of-a-figure|More details]] | * a Matplotlib **//Axis//** is a **plot** inside a Figure... [[http://matplotlib.org/faq/usage_faq.html#parts-of-a-figure|More details]] | ||
* reserve space for **one plot** that will use most of the available area of the figure/page: | * reserve space for **one plot** that will use most of the available area of the figure/page: | ||
- | * ''my_plot = my_page.add_subplot(1, 1, 1)'': syntax is ''add_subplot(nrows, ncols, index)'' | + | * ''my_plot = my_page.add_subplot(1, 1, 1)'' or ''my_plot = my_page.subplot**s**()'' |
- | * ''my_plot = my_page.subplot**s**()'' | + | * the syntax for **more than one plot** is: ''add_subplot(nrows, ncols, index)'' |
* create **3 plots on 1 column** (each plot uses the full width of the figure): | * create **3 plots on 1 column** (each plot uses the full width of the figure): | ||
* <code>top_plot = my_page.add_subplot(3, 1, 1) | * <code>top_plot = my_page.add_subplot(3, 1, 1) | ||
- | middle_plot = my_page.add_subplot(3, 1, 2) | + | mid_plot = my_page.add_subplot(3, 1, 2) |
- | bottom_plot = my_page.add_subplot(3, 1, 3)</code> | + | bot_plot = my_page.add_subplot(3, 1, 3)</code> |
- | * the following method is more efficient than add_subplot when there are lots of plots on a page<code>plot_array = my_page.subplots(3, 1) | + | * creating an //array of plots// with ''subplots'' is **more efficient** than ''add_subplot'', when there are lots of plots on a page<code>plot_array = my_page.subplots(3, 1) |
top_plot = plot_array[0] | top_plot = plot_array[0] | ||
- | middle_plot = plot_array[1] | + | mid_plot = plot_array[1] |
- | bottom_plot = plot_array[2]</code> | + | bot_plot = plot_array[2]</code> |
- | * creating a figure and axes with a single line: ''my_page, plot_array = **plt**.subplots(3, 1)'' | + | * it is **even more efficient** to create a //figure// **and** //axes// with a single line: |
+ | * one plot on one page: ''my_page, my_plot = **plt**.subplots()'' | ||
+ | * three plots on one A4 portrait page:\\ <code> | ||
+ | my_page, plot_array = plt.subplots(nrows=3, ncols=1, | ||
+ | figsize=(8.3, 11.) # A4 portrait) | ||
+ | top_plot = plot_array[0] | ||
+ | mid_plot = plot_array[1] | ||
+ | bot_plot = plot_array[2] | ||
+ | </code> | ||
+ | * if you need to specify the same additional //keyword// parameters (that will be passed //behind the scene// to the ''add_subplot'' function), you can use the ''subplot_kw'' parameter. For example, if all the plots will be created with cartopy, using the //Robinson// projection, the example above becomes:\\ <code> | ||
+ | my_page, plot_array = plt.subplots(nrows=3, ncols=1, | ||
+ | figsize=(8.3, 11.), # A4 portrait | ||
+ | subplot_kw=dict(projection=ccrs.Robinson())) | ||
+ | </code> | ||
* use [[https://matplotlib.org/api/_as_gen/matplotlib.figure.Figure.html#matplotlib.figure.Figure.add_axes|my_page.add_axes(...)]] to add an axis in an arbirary location of the page\\ ''my_page.add_axes([left, bottom, width, height])'' | * use [[https://matplotlib.org/api/_as_gen/matplotlib.figure.Figure.html#matplotlib.figure.Figure.add_axes|my_page.add_axes(...)]] to add an axis in an arbirary location of the page\\ ''my_page.add_axes([left, bottom, width, height])'' | ||
* a Matplotlib **//Artist//** or //Patch// is //something// (e.g a line, a group of markers, text, the legend...) plotted on the Figure/Axis | * a Matplotlib **//Artist//** or //Patch// is //something// (e.g a line, a group of markers, text, the legend...) plotted on the Figure/Axis |