What is Classification? What is a Classifier?

00:06:41
https://www.youtube.com/watch?v=SAUIDEhGC8w

Resumen

TLDRThe video provides an introduction to classification in data mining, explaining its role in predicting categorical variables based on input data. It discusses the process of building models using numerical and categorical variables, referred to as predictors or features. The importance of understanding linear and nonlinear separability is emphasized, with examples illustrating how to visualize data. The video also mentions transforming multi-class problems into binary classification and outlines classifiers that will be covered in future videos, such as ZeroR, OneR, and Naive Bayes.

Para llevar

  • 📊 Classification predicts categorical variables.
  • 🔍 Models can use numerical or categorical variables.
  • 📈 Linear separability allows perfect class separation.
  • 🔄 Nonlinear separability means classes overlap.
  • 🔄 Multi-class problems can be converted to binary.
  • 📝 Diagrams aid in visualizing data concepts.
  • 🔄 Numerical data can be transformed to categorical.
  • 🔄 Upcoming classifiers include ZeroR and Naive Bayes.
  • 📚 Understanding features is crucial for classification.
  • 🔍 Focus on binary classification in this series.

Cronología

  • 00:00:00 - 00:06:41

    In this video, the concept of classification in data mining is introduced, focusing on predicting categorical variables, also known as classes or targets. The process involves building a model using one or more numerical or categorical variables, referred to as predictors, descriptors, or features. The speaker emphasizes the importance of transforming data types, such as converting numerical data to categorical and vice versa, and mentions a well-known dataset with features like outlook, temperature, humidity, and windiness to illustrate classification. The video also discusses linear and nonlinear separability of data, using height and weight as an example, and explains how to handle binary and multi-class classification problems. The speaker outlines upcoming topics, including various classifiers and the significance of visual aids in understanding data separability.

Mapa mental

Vídeo de preguntas y respuestas

  • What is classification in data mining?

    Classification is a data mining task that predicts the value of a categorical variable, also known as a target or class.

  • What types of variables can be used in classification?

    Both numerical and categorical variables can be used to build classification models.

  • What is linear separability?

    Linear separability refers to the ability to perfectly separate two classes with a straight line in a 2D space.

  • What is nonlinear separability?

    Nonlinear separability occurs when classes cannot be perfectly separated by a straight line.

  • How can multi-class problems be transformed?

    Multi-class problems can be transformed into binary classification problems using techniques like one-vs-all.

  • What classifiers will be covered in upcoming videos?

    Upcoming videos will cover classifiers like ZeroR, OneR, Naive Bayes, Decision Trees, Linear Discriminant Analysis, Logistic Regression, K-Nearest Neighbors, and Neural Networks.

  • What is the importance of diagrams in classification?

    Diagrams help visualize data and understand concepts like linear and nonlinear separability.

  • How can numerical data be transformed into categorical data?

    Numerical data can be transformed into categorical data through techniques like binning or discretization.

  • What is the focus of this video series?

    The series focuses on binary classification and various classifiers used in data mining.

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Desplazamiento automático:
  • 00:00:01
    welcome back in this video we'll start
  • 00:00:03
    explaining what classification is and uh
  • 00:00:08
    give a brief introduction of what the
  • 00:00:10
    process of classification entails now
  • 00:00:14
    classification is a data mining task of
  • 00:00:16
    predicting the value of a categorical
  • 00:00:19
    variable sometimes it's called the
  • 00:00:20
    Target or a class so here we have some
  • 00:00:23
    input data we have some data sets with
  • 00:00:25
    instances one or more data sets with
  • 00:00:28
    instances I e with columns
  • 00:00:32
    um uh different columns and different
  • 00:00:34
    values and then we want to predict a
  • 00:00:37
    categorical variable iea class now this
  • 00:00:40
    is done by building a model based on one
  • 00:00:43
    or more numerical or categorical
  • 00:00:45
    variables so our variables can be
  • 00:00:47
    numerical or categorical and we can use
  • 00:00:50
    one or more of them or maybe none of
  • 00:00:52
    them as you will see to build that model
  • 00:00:55
    these variables or these descriptors
  • 00:00:58
    sometimes they're known as predictor
  • 00:01:00
    sometimes they're known as uh
  • 00:01:02
    descriptors or attributes or features
  • 00:01:05
    they all mean the same
  • 00:01:07
    thing now one thing I'd like you to
  • 00:01:09
    remember always and as you will see from
  • 00:01:12
    my videos that sometimes I give you
  • 00:01:14
    examples for example with data which
  • 00:01:16
    only contains variables of categorical
  • 00:01:19
    type if you want to apply the same
  • 00:01:21
    algorithm and you have data which
  • 00:01:23
    contains numerical numerical variables
  • 00:01:25
    then you can transform numerical to
  • 00:01:28
    categorical and you can transform
  • 00:01:30
    categorical to numerical so other way
  • 00:01:33
    around if you not if you don't know how
  • 00:01:35
    to do this then please watch my data
  • 00:01:37
    exploration and Analysis uh uh tutorial
  • 00:01:41
    in there I explain these uh Concepts
  • 00:01:44
    binning or discretization to to
  • 00:01:47
    transform from numerical to categorical
  • 00:01:48
    and I explain encoding or continuation
  • 00:01:52
    to transform from categorical to
  • 00:01:55
    numerical just to give an example this
  • 00:01:57
    is a data set well known we the
  • 00:02:00
    Set uh we have four features or four
  • 00:02:04
    descriptors or I'm sorry four predictors
  • 00:02:06
    Outlook temperature humidity windy and
  • 00:02:09
    you can not that all of them are of type
  • 00:02:12
    categorical and here we have our class
  • 00:02:15
    which is now play golf either yes or no
  • 00:02:17
    and not it's again it's actually a
  • 00:02:18
    categorical variable and this tree
  • 00:02:20
    diagram here just shows us that the
  • 00:02:22
    yellow box here is the class so we're
  • 00:02:25
    trying to decide whether to play or not
  • 00:02:27
    to play based on
  • 00:02:30
    uh values from our attributes or from
  • 00:02:32
    our features or from
  • 00:02:34
    our uh predictors now one thing I'd like
  • 00:02:37
    you to familiar with is the linear
  • 00:02:40
    nonlinear separability and always please
  • 00:02:44
    always remember to use diagrams diagrams
  • 00:02:47
    help us greatly to visualize things so
  • 00:02:49
    we can have a feel of what the data
  • 00:02:52
    looks like
  • 00:02:53
    and um uh how we can go about our data
  • 00:02:58
    now let's assume for example that we
  • 00:03:00
    take some measurements from people
  • 00:03:01
    randomly we measure for example height
  • 00:03:04
    and uh weight and let's assume that we
  • 00:03:07
    plot height and weight against each
  • 00:03:10
    other in this 2D diagram as you can see
  • 00:03:12
    let's assume that weight is the y- AIS
  • 00:03:15
    and height is the x-axis and let's
  • 00:03:17
    assume that uh the red dots here are
  • 00:03:20
    males and the blue dots are females now
  • 00:03:23
    you can see that we can nicely draw a
  • 00:03:26
    straight line that perfectly separates
  • 00:03:28
    the two categories or the two classes
  • 00:03:31
    this data set or this data is set to be
  • 00:03:33
    linearly separable if there's overlap
  • 00:03:37
    and we can't draw a straight line to
  • 00:03:39
    perfectly split the data then that's
  • 00:03:41
    known as non non non nonlinearly
  • 00:03:45
    separable
  • 00:03:46
    data um now you notice here we have only
  • 00:03:49
    two classes let's say maybe male or
  • 00:03:51
    female sometimes we can have more than
  • 00:03:53
    two classes and we can transform that
  • 00:03:55
    into a binary classification Problem by
  • 00:03:58
    the way I will be only f focusing on
  • 00:04:00
    binary classification so the class
  • 00:04:02
    should be yes or no maybe positive
  • 00:04:04
    negative true or false 0 1 or minus one
  • 00:04:07
    + one or something like that if we have
  • 00:04:09
    a problem with multiple classes then we
  • 00:04:11
    can transform it into a binary Problem
  • 00:04:14
    by for example using the one against all
  • 00:04:16
    technique or any other
  • 00:04:19
    technique again to show you a
  • 00:04:21
    nonlinearly separable data here we can't
  • 00:04:24
    actually draw a straight line to
  • 00:04:26
    perfectly uh separate the two classes
  • 00:04:28
    but there are some the tricks where we
  • 00:04:31
    can transform the data now from from
  • 00:04:33
    these uh from the dimension we have now
  • 00:04:36
    that we have now two dimensional data
  • 00:04:38
    let's say weight and height only two
  • 00:04:40
    Dimensions we can add more Dimensions so
  • 00:04:43
    we can split that data by the way if the
  • 00:04:46
    data is two dimensional I.E only we only
  • 00:04:49
    have two measurements or two attributes
  • 00:04:51
    or two features then uh we can draw a
  • 00:04:54
    line if the data is threedimensional
  • 00:04:56
    then we can draw a plane if the data is
  • 00:04:59
    is more than threedimensional it becomes
  • 00:05:01
    a hyper
  • 00:05:03
    plane and um the good thing is that
  • 00:05:06
    anything you can do in 2D if you can
  • 00:05:09
    draw a line in 2D then you should be
  • 00:05:11
    able to draw a plane in 3D or a hyper
  • 00:05:14
    plane in more than 3D we won't go in
  • 00:05:17
    into much detail uh uh uh for for the
  • 00:05:21
    math behind it but you can uh trust that
  • 00:05:25
    that that can be done now the upcoming
  • 00:05:28
    videos for classification will uh we
  • 00:05:30
    will be covering these classifiers zero
  • 00:05:33
    r one R naive Bas and decision decision
  • 00:05:35
    tree which are based on frequency table
  • 00:05:38
    we'll be covering line linear
  • 00:05:40
    discriminant analysis and logistic
  • 00:05:41
    regression which is based on covariance
  • 00:05:43
    Matrix we'll be covering the K nearest
  • 00:05:46
    neighbor uh uh classifier which is based
  • 00:05:48
    on similarity functions and we'll be
  • 00:05:50
    covering artificial neural networks and
  • 00:05:52
    support Vector support vect the
  • 00:05:55
    machines uh what else uh just remember
  • 00:05:59
    always to use diagrams remember this
  • 00:06:02
    concept of linear separability and N
  • 00:06:05
    nonlinear separability the problem of
  • 00:06:07
    binary classification when we have only
  • 00:06:09
    two classes if we have multi classes
  • 00:06:10
    then we can transform it into a binary
  • 00:06:12
    classification using the one versus all
  • 00:06:15
    concept and always remember that if your
  • 00:06:19
    algorithm uh applies to categorical
  • 00:06:22
    variables or categorical attributes then
  • 00:06:24
    we can transform them into uh and and we
  • 00:06:27
    have numerical data then we can
  • 00:06:28
    transform them using encoding and the
  • 00:06:31
    opposite is always true I will I will
  • 00:06:34
    stop here in the next video I'll be
  • 00:06:35
    introducing the Zer R classifier thanks
  • 00:06:38
    for watching and I'll see you next time
Etiquetas
  • classification
  • data mining
  • categorical variable
  • predictors
  • linear separability
  • nonlinear separability
  • binary classification
  • multi-class problems
  • data visualization
  • machine learning