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## What does int IV mean?

Intermittent Needle Therapy

## What is a principal component in PCA?

Principal component analysis (PCA) is a technique for reducing the dimensionality of such datasets, increasing interpretability but at the same time minimizing information loss. It does so by creating new uncorrelated variables that successively maximize variance.

## How do you find the principal component?

Step by Step Explanation of PCA

1. Step 1: Standardization.
2. Step 2: Covariance Matrix computation.
3. Step 3: Compute the eigenvectors and eigenvalues of the covariance matrix to identify the principal components.

## What is the first principal component?

The first principal component (PC1) is the line that best accounts for the shape of the point swarm. It represents the maximum variance direction in the data. Each observation (yellow dot) may be projected onto this line in order to get a coordinate value along the PC-line.

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## What is PCA algorithm for face recognition?

PCA is a statistical approach used for reducing the number of variables in face recognition. In PCA, every image in the training set is represented as a linear combination of weighted eigenvectors called eigenfaces. These eigenvectors are obtained from covariance matrix of a training image set.

## When should you not use PCA?

PCA should be used mainly for variables which are strongly correlated. If the relationship is weak between variables, PCA does not work well to reduce data. Refer to the correlation matrix to determine. In general, if most of the correlation coefficients are smaller than 0.3, PCA will not help.

## How do you do a PCA?

Steps Involved in the PCA

1. Step 1: Standardize the dataset.
2. Step 2: Calculate the covariance matrix for the features in the dataset.
3. Step 3: Calculate the eigenvalues and eigenvectors for the covariance matrix.
4. Step 4: Sort eigenvalues and their corresponding eigenvectors.

## What are the circumstances Data or Analyses where you should use PCA?

PCA technique is particularly useful in processing data where multi-colinearity exists between the features/variables. PCA can be used when the dimensions of the input features are high (e.g. a lot of variables). PCA can be also used for denoising and data compression.

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## What are the steps in preprocessing before applying PCA algorithm?

1. Steps Involved in PCA. Standardize the data. (
2. 2.1 Covariance Matrix.
3. 2.2 Eigenvectors and Eigenvalues computation from the covariance matrix.
4. 2.3 Eigen Vectors verification.
5. 3.1 Sorting eigenvalues.
6. 3.2 Explained Variance.
7. Visualize 2D Projection.

## How do you select the number of components in PCA?

Choosing the number of components A vital part of using PCA in practice is the ability to estimate how many components are needed to describe the data. This can be determined by looking at the cumulative explained variance ratio as a function of the number of components: In : pca = PCA().

2021-05-27