YouTube Transcript:
Introduction to Line Plot Graphs with matplotlib Python

okay this is gonna be an introduction to
line plots with matplotlib and Matt plot
led is the primary graphics library for
Python it's a third-party library but
it'll be installed automatically if you
have installed a scientific platform
such as anaconda now there are many
other graphics libraries out there but
most of them are just wrappers around
matplotlib so in other words they use
matplotlib as the base case and
matplotlib allows the production of
publication quality graphics now if you
consider all of the elements of a graph
the axes the labels the plot area you
can just imagine that it may take many
lines of code to get some of your grass
looking just the way you want them now
this is going to be an introduction to
line plots and I'm gonna cover most of
the common elements in the graph so you
can get started so I'm gonna be working
with a jupiter notebook here and you're
gonna be able to download this notebook
from a link in the video the first thing
we're gonna need to do is to set up the
environment the only library I really
need here is matplotlib but I'm going to
import pandas and pandas data reader so
that I can work with some real data
now matplotlib is a huge library and it
has lots of modules within it the main
module you're gonna want to work with is
PI plot and so that's what I'm going to
import okay we'll run that cell okay and
then I'll go ahead and get some date I'm
gonna get some stock price data for
Google and Amazon and then we'll just
take a look at the first few rows of
that okay so I have data going back to
the beginning of 2019 here and with that
we're ready to go ahead and start
plotting so at the most basic level all
we need to do is call that import PLT
and then call plot so plot is the main
line plot method and then I'll just
reference what I want to plot okay so
you can see we get a very basic graph
alright another artifact we get is the
reference to the object we created we
can suppress this with a semicolon
okay if we want to plot the Amazon with
the Google
we just go ahead and add another line
okay and this gives you an example of
how the pipe lot module works
essentially what we're doing is we're
building these graphics in layers and so
Python always assumes that we are
talking about the current graph so
anything that I reference here is gonna
get added to this current graph alright
so we'll make a few other changes
because this is looking pretty boring
one of the first things we're going to
do is make the graphic larger so I'm
going to import another module from
matplotlib
okay this is going to allow us to set
certain parameters so I'll set the
figure size okay the parameters actually
live in a list like structure
okay so we'll see what that does okay so
we get a larger graphic if you want to
play around with the height and width we
can do that all right so at least now we
can see the dates clearly all right and
then let's add a few more features to
our graph okay I'm always gonna end with
this semicolon so I suppress that object
address all right so the next thing I'm
gonna do is add the legend and if I
don't give it any location it's gonna
show up in the upper right here all
right and I can change the location
there's lots of ways to do it I tend to
use the numeric system
all right so location 2 is upper left so
that's location 1 2 3 and 4 we can set
it in the middle so location 6 in the
middle there and I can get it on the
other side okay and then along the
horizontal axis we can Center it there
as well all right in the top or the
bottom so location 9 all right so I said
it as location 2
all right next thing we're gonna do is
add some lines in here so these things
are not just kind of floating in space
so I'm going to call the grid and I'm
gonna set it as true ok so by default we
just get this sort of grayscale line you
can control it a little bit so we can do
something like set the color you can set
the color as anything you want there are
seven color codes CMYK GRB all right so
I'll just set it as black okay so that
basically makes the grids take the front
stage here all right so they're sort of
featured more prominently than any of
the data we're graphing I'm going to
change their line style
and there are a few line styles so we
can do a dashed line and dash dot a dot
dot is what I'm about to do I'm paying
so then that I guess makes the data
front and center again what would your
graph be without a title so we're gonna
add a title
so just like that we have a title we
could if we wanted to set the font we
could set a different font we can set a
different font size okay there's lots of
options I'm not gonna be able to go
through here in a quick video okay if we
want to label the axes I can set X label
or Y label here I'll just set the X and
we'll get date down there okay if we
want to play around with the limits of
our axes either X or Y we can set limits
so I will do this quickly just to
demonstrate it for the y axis
okay the property is either x limb or Y
limb we need to tell it where to start
and where to stop so we'll go down to
500 and up to 2500 just so we get a
different axes here it's not probably
gonna look very good okay so there it is
it kind of centers the data there all
right if we don't want to see all of
these ticks all right we can set a limit
so Y ticks X ticks all right and then
it's going to take a list like structure
so I can set a variable pass this into X
ticks and so I can just start at 500 and
go every 500
all right a couple more things if we had
a line style that we can use for the
grids we must have one that we can use
on the actual data and we do all right
so I will play with the data just a
little bit and I'll make it read all
right so this sort of a shortcut method
of setting the color and the line style
all right I can break them out and
specify it if I want I can use OHS
alright so I get a bigger dot there
alright and so as I mentioned there are
seven colors you can use with the
shortcut method CMYK RGB if you want
some other color you can specify a color
and you can actually use any system
alright so I can use blue okay Python
has a number of built-in colors so
something like Alice blue would work
alright I can use a hexadecimal color so
okay so there's a hex code I can use RGB
using three coordinates between zero and
one that indicate how close to black I
want to get okay the most common thing
you probably do is just let matplotlib
decide what the color will be all right
so that's what I did when I first
started I just let matplotlib decide
what the default should be okay and if
we want to get something that's a little
bit awed mented here we can import a
different theme to plot
okay so there's a number of styles we
can use I'm going to try ggplot alright
so there's a common wrapper library that
you can also install and work with if
you don't want to work with matplotlib
okay we see it looks pretty much the
same as the default so we'll get
something that looks a little bit
different here and yeah if you're
wondering and you're familiar with our
that is the same ggplot that is the sort
of de facto standard in our alright let
me try a different style here okay so
there's the 538 style and as I mentioned
at the beginning a lot of times getting
your graphics to look just right takes
lots of lines of code alright we haven't
really done that much but you can see
that oh there are quite a few lines of
code here just to get a pretty simple
graph out there alright so that's why
maybe you should take a look at some of
the themes and see if any of those will
at least get you to a baseline that you
can work from okay and then down below
here I have included a couple of links
out to the documentation the
documentation is very good and extensive
so you can spend a lot of time out there
I just pointed at the common things that
you might want to do like look at the
different themes okay so we can scroll
through and we can set one of these to
be used instead of the default all right
and there are quite a few alright and
the interesting thing here is down at
the bottom they actually show you the
code that they use to generate these
this graphic up above alright so if you
want to get a little bit more exposure
you can take a look at this and even try
that code okay and then just I showed
you one quick line marker or two I guess
I showed you the dots and the and the
O's here's the extensive listing of all
the different markers you can use
alright so that would be a line style
okay so I hope that can get you started
with line plots and matplotlib