Regression Training and Testing - Practical Machine Learning Tutorial with Python p.4 Video Lecture | Machine Learning with Python - AI & ML

What is going on everybody welcome to the [fourth] machine learning and third regression tutorial where we left off we had defined
Our or at least figured out what [our] features in our labels were we haven't quite [yet] defined them, but in this one
We're going to define them
We're going to actually pass them through to a classifier train and test that classifier to see how we do
So before we get started let's go [ahead] make some imports [also]
I'm just going to put kwan Deland math on the same line now
We're going to go ahead and import numpy as NP numpy is just a nice
Computing library it's going to allow [us] to use arrays python doesn't actually have arrays, but numpy will let us do that
Also from Sk Learn we're going to import
Pre-processing this gives us quite a few things, but we're actually going to be using the scaling
scaling your data aspect is usually done [on] the on the features and
The goal is often to get your features to be between somewhere between negative 1 and a positive 1 this can just help with
Accuracy as well as just processing speed or how long it might take to actually do the calculations
When we get there?
I'll explain why you may actually just either
Choose not to do pre-processing or maybe it's just [too] you know too tedious to incorporate it in reality, but anyway
We'll show it because it exists and it can be useful
Next is cross-validation
We're going to use cross-validation to create our training and testing samples. It's just a really nice way to split up your data
into
it'll shuffle your data for you, and which helps with that with
Statistics basically so you don't have a biased sample [and] then also it helps separate your data
It's just nice time-saver basically and we're also going to bring an SVM
[that] we're not to the support vector machine part, and we're not I'm not going to explain support vector machines just yet
We will get there, but you can use an Svm to do regression
and this is probably we are probably not going to come back to regression, so
We'll just show it as an example using it.also
It's useful because I'll show you how [frigging] simple it is [to] change the algorithm that you're using so anyways Svm
Next we're actually gonna bring in regression so from Sk learn
dot
Underscore Model Import Linear Whoops linear
Regression okay now. We are [ready] [to]
Rhumble so the first thing that we're going to go ahead and do is define our x and y [so] generally features and labels are
Defined features will be a capital x labels will be a lowercase y x is going to be equal to numpy array
of
Df Drop and we're going to drop
the
Label Column right, so your features are basically everything
Except for the label Column and we can do this because df drop
Returns a new data frame so it's returning a new data frame. It's can being converted to [a] numpy array
it's being saved to the value of x
Now the value of y is our labels, so you might be able to surmise that we're going to say Mp. Dot array
df
label
easy enough
Okay, so now we're going to scale x so x equals
pre-processing dot scale
X okay now think about it. So here
We're scaling x before we feed it [through] the classifier, but let's say we feed it through a classifier
We have a classifier, and then we're using it in real time on real data
well, let's say you're reading in that data and
You feed it through your classifier, but before you do that. You really have to have scaled it and to scale it
It's all scaled together, so it's like normalized with all the other data points
So in order to properly scale it you would have to include it with your training data
So keep that in mind if you ever go into the future and you're actually using this you need to scale the new values
But not just scale alone, but scale them alongside all your other
values, so this can add action while it can help with the training and testing it can actually add to processing time especially if
You're doing like any sort of like for example, but with using stock prices
You're doing like high-frequency trading you would almost certainly skip this step, but anyway
There's that now we're going to redefine x as being equal
to x
to the point of where [we] got where we were able to forecast underscore out [+1]
So this is is it includes all the points because remember we shifted to you know this point zero [one]
You know so [that's] like
What [1%] basically so we made [that] shift so we just want to make sure that we only have x's where we have values for?
y and
so we do that, and then we're going to say d f dot drop in a
in
place equals true, and then we're going to do we're going to Define [y] is equal to np [r] [a]
df
label and
Let's go ahead and let's print
Lem of X and then len of y, so, just make sure we have the correct lengths here
right so we don't have the correct [lengths] so let's close this and
Really probably at this [point]. So we actually may not need to have this let me rerun that real quick
So I'm thinking yeah okay, so so because we won't have [a] label for
The reason why I was doing this shift initially was because we wouldn't actually have labels
But we dropped those labels here are those those rows here? So we didn't need to do what we were doing there, okay?
so we've got our x's on our y's and
We don't need this hopefully
Okay, so now what we're ready to do is create our training and testing sets, so we're going to say x underscore
Train x
underscore
Test why Underscore train why underscore test?
equals
cross-validation
dot train underscore test underscore split and
What you're going to pass through here is the x's the y's and then how big of a test size
Do you want and we're going to do point two so [20%] of the data?
We want to actually use as testing data
so again what this is going to do is is going to take all our features on our labels remember kind of the order it's
going to shuffle them up right keeping x's and y's
Connected right so it's not going to shuffle them up to the point where you lose
Accuracy, so it shoves them up, and then it outputs
for x training Data wide training Data x testing data and y testing data so x training y train we use to
Fit our classifiers, so let's do that next so first we're going to need to find a classifier
so we're going to say classifier equals, and we'll use linear regression to start and
Then to fit or train a classifier. Just see a left fit and you fit
features and labels, so which ones should we use well we would use the x
Train and y train
Now we've got our classifier. We can [actually] use this classifier to predict into the future do all kinds of crazy stuff
But first we probably should test it, right
200C is so now what we would say is Cl. F dot score
so fit is synonymous with train score is synonymous with test, so we'll use x
Test y test so real quick why might you want to train and test on separate data?
Well if you train a classifier to predict based on the same data that you test against when you go to test it
It's going to be like I've already seen this information, so I know exactly what the answer [is] right
So that's not good. You don't want to do that. It's no different than if [you] know if you were in school, or whatever and
you were
The same questions that you were asked in
Class were the exact identical questions on a test right if you missed those then you just weren't paying attention or something
So here we have our score and what we're going to say is
Thence equals Cl f. Dot score you could also maybe replace confidence with accuracy
accuracy
that's probably a better choice because confident you not only you can kind of get to values not necessarily from this one, but
As we go into the future
[you] can actually compute both accuracy and confidence
As two different values so we'll go ahead and keep accuracy there and let's print
Accuracy, so let's save and run that
wait for root and
the accuracy that we got out of this is 0.96 so
[ninety-six] percent accuracy on predicting what the price would be
Shifted one percent of the days, so this would be let's go ahead and print
Forecasts out so we can see what that value actually is
So with linear regression just four just so you know
The accuracy is going to be the squared error, and we'll talk about that
Coming up next as we break down. How linear regression actually works, so this is actually still 30 days in advanced
So it's pretty interesting that you'd still be that accurate [but] okay
[so] it's okay. Yeah
so now
what if though
[A]
Couple things first of all its squared error, so this this actual percentage of accuracy is not
Necessarily like [you] would get rich off this algorithm. It's almost like
Maybe directionally accurate, but that's actually that's pretty darn pretty darn accurate
So let's say though remember. I what we also brought in Svm. Let's say we wanted to use the
support vector regression, which is not
Simple linear regression, so we're not going to actually break down, but what if we wanted to use [a] [different] algorithm?
So we're using linear regression. Here's how easy it is to switch our algorithm SvMs
B are
done
so now we're testing a new algorithm, and
This one does actually [a] lot worse wow let's run that more time. Let's see if it still is inaccurate
Yeah, wow
That's that's interesting. That's a huge difference
[anyway], you will actually kind of find that that happens now
for example [in]
With machine learning like with support vector regression for example you have these things called Kernels
So you might say Kernel kernel equals. I want to say the default is
linear so let's try a polynomial
Kernel so you can change these Kernels in there?
And you can kind of fiddle with [it] and see if you could get better values. [oh] my gosh, so
51% accuracy is like just barely better than average or better barely better than like clique coin toss
Let's see if we can actually get under 50
No, wow, that's that's a significant Variance. Oh goodness
Anyway, as we can see [it's] [e] support vector regression is not what we're going to be using in this case anyways
But so here's another decent example about why you'd want to follow this tutorial series though like what's a Kernel [alright]
So we'll be explaining. What a kernel is when we get to support vector machines, but anyway
what this was meant to show is how easy it is to switch between
clatter
Algorithms and this is the case whether you're doing regression, or whether you're doing classification or clustering you can switch out rhythms really quick
So you you definitely want to like test the algorithms oops do we do oh Svm linear regression?
Okay, so anyways. There's that one more thing to talk about
Before I let you guys go is
with the various algorithms you'll want to check the
documentation so let me pull up the documentation for linear regression for example and
What you're looking for is which algorithms can [be] threaded
So in this case
we [are] looking for and
Underscore jobs this the question is how many jobs can we perform at any given time and so?
Right now it may not be totally obvious to you. Why?
with
Let's say linear regression
We can thread the heck out of linear regression as opposed to a support vector machine where?
There are ways that you could do it
You could like do it in batches or something there are ways that you [could] do it
But it's just not inherently as easy as something like regression is to thread it
Massively and run it in huge parallel operations, but with regression. It totally is and you'll see why
Later on but anyway, so yeah
So this is just so if if you were following along, and let's say you're skipping the true breakdowns shame on you
but but to find out if it really quickly if the algorithm
Could be threaded you would just go to the page right you can just search linear regression support vector machine on Google
You'd find yourself on this page, and you're looking for N
Jobs, so this just means how many jobs how many threads are we willing to run at any given time?
So the default let me think here so the default for regression is actually 1
so this means it's running in I
Hate to use the word linear here, but it is running linearly right whereas we could run it in parallel by doing N
Jobs equals, and you could say okay?
[I] want to run at least ten jobs at a time
so I will run ten jobs at a time and in theory the training and testing part actually I'm sorry just the
Training part would be significantly faster
[or] you can use negative one and this will just run as many jobs as
As possible by your your processor
so
Anyway speaking of which processor wise as you follow along this series if you get to a point where like I'm getting it really fast
And you're going really slow like if you're following on like an older computer or a laptop or something like that
[it] may take you a little longer to run some of these things this one should [be] pretty quick
But it's conceivable especially when we get into like deep learning you might want to think about
Spinning up a server or something like that, but that's obviously way down the line
Well, we'll talk about it when we get there. I suppose, but just keep that in mind
So anyways just remember this, but then again just one more
Plug about why you'd want to dig in deep which we're about to be doing is
To understand which algorithms you can do this with so exam for example with deep learning
Like linear regression, not just in deep learning like all the algorithms really. There's a lot of regret a lot of like linear
Algebra that goes in because a lot of these things can be
Super threaded and you can run many operations at once and like so as we grow [in] processing power that becomes very useful to have
Calculations and methodologies that can that can scale like that
Anyway, that's it here in the next tutorial. We're going to be talking about predictions into the future
Using Scikit-learn and then after that we'll actually going to be breaking down linear regression and doing it ourselves
so stay tuned for that if you have questions comments concerns or whatever up to this point feel free to leave them below otherwise as
Always thanks for watching thanks for all the support and subscriptions, and it's he'll next time