Machine Learning MLE - Data Pre-processing & Feature Analysis

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Questions and Answers

What is one of the methods used for data imputation?

  • Using mean or median values (correct)
  • Excluding all features with missing data
  • Generating synthetic data
  • Random sampling from dataset

Why is the curse of dimensionality a concern in machine learning?

  • Data samples become too sparse in the feature space. (correct)
  • It simplifies the model training process.
  • It makes algorithms run faster.
  • It leads to a loss of important features.

What is a common strategy to avoid the curse of dimensionality?

  • Increase the number of data samples (correct)
  • Use only one feature for analysis
  • Increase the number of irrelevant features
  • Ignore dimensionality issues completely

Which of the following techniques can be used for dimensionality reduction?

<p>Feature selection (A)</p> Signup and view all the answers

What can be done if an algorithm panics when encountering missing data?

<p>Use a method to impute missing values (A)</p> Signup and view all the answers

What is the primary goal of data normalization in machine learning?

<p>To improve numerical stability of the model (C)</p> Signup and view all the answers

Which of the following is NOT a method of data normalization?

<p>Standardization (C)</p> Signup and view all the answers

What might be a consequence of not normalizing feature values before training a machine learning model?

<p>Imbalance in learning rate effectiveness among features (B)</p> Signup and view all the answers

Which visualisation technique is best for exploring relationships between two continuous variables?

<p>Scatter plot (A)</p> Signup and view all the answers

What does one-hot encoding primarily facilitate in machine learning?

<p>Encoding categorical variables for model input (A)</p> Signup and view all the answers

Which of the following statements about data preprocessing is accurate?

<p>It addresses missing data and data errors. (D)</p> Signup and view all the answers

What does Z-Normalisation rely on for its calculations?

<p>Mean and standard deviation of the dataset. (B)</p> Signup and view all the answers

What is the primary purpose of visualizing data before processing it?

<p>To understand the underlying problem and detect outliers (C)</p> Signup and view all the answers

Flashcards

Data Imputation: Removing instances with missing features

Removing data points with missing features. This is often a safer approach when you have a large dataset.

Data Imputation: Mean/Median/Mode Imputation

Replacing missing values with the average or most frequent values.

Data Imputation: Machine Learning-Based Imputation

Using a machine learning model to estimate missing values based on other features.

Curse of Dimensionality

The challenge of having too few data points compared to the number of features, causing sparse data distribution.

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Feature Selection and Dimensionality Reduction

Reducing the number of features to combat the curse of dimensionality.

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Data Preprocessing

Understanding and preparing data for machine learning models. This includes tasks like cleaning, transforming, and scaling data, which are often necessary for optimal model performance.

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Feature Representation

The process of selecting and representing information about an instance (data point) in a meaningful way for machine learning. It involves using a set of features that accurately describe the underlying problem and can be used by the learning algorithm.

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Boxplot

Visualizations that display the distribution of continuous data, showing outliers, minimum, maximum, median, and quartiles. They are helpful for identifying the spread and potential issues with data sets.

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Histogram

A visual representation of the distribution of categorical data. Helpful for understanding the frequency of each category and identifying potential imbalances in the data.

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Scatter Plot

A visual representation that displays the relationship between two variables. Useful for understanding the correlation, trends, or patterns between variables. A scatter plot can highlight potential outliers or linear relationships.

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One-Hot Encoding

A technique used to transform categorical features into a numerical representation. It involves creating a binary vector for each category, where each element represents the presence or absence of the category.

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Z-Normalisation

Normalizes feature values to have zero mean and unit variance. Useful for improving the stability and performance of algorithms that rely on distance calculations.

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Min-Max Normalisation

Normalizes features by scaling them within a specified range. Often uses the 5th and 95th percentiles to avoid the influence of outliers.

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Study Notes

Machine Learning (MLE) - Data Pre-processing & Feature Analysis

  • Machine learning processes data using a pipeline including data representation, modeling, evaluation, and optimization.
  • Data understanding involves grasping the underlying problem and visualizing data characteristics like outliers and value ranges.
  • Feature representation focuses on reliability and categorizing features as categorical, binary, or continuous.
  • Feature value normalization ensures features are appropriately scaled.
  • Preprocessing addresses missing data and errors using strategies like data imputation.
  • Data visualization techniques like boxplots, histograms, and scatter plots help understand and analyze data patterns.
  • Categorical data can be converted using one-hot encoding.
  • Data normalization methods include Z-normalization (zero-mean normalization), min-max normalization, and vector normalization.
    • Z-normalization calculates deviations from the mean and standard deviation.
    • Min-max normalization scales data within a specific range.
    • Vector normalization scales data to unit length.
  • Advantages of data normalization include maintaining original data distribution, improved model numerical stability, and lessened impact on distance-based algorithms.
  • Data imputation methods fill in missing data using approaches like using mean/median values, frequent values, k-nearest neighbors, multivariate imputation, and machine learning models.
  • Curse of dimensionality occurs when the number of data instances is insufficient compared to the number of features, leading to sparse data and reduced model effectiveness.
  • To mitigate the curse of dimensionality, increasing the number of data samples or reducing the number of features is crucial
    • Feature selection and dimensionality reduction techniques are employed to achieve this.

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