An overview of the Multivariate toolset

Available with Spatial Analyst license.

Multivariate statistical analysis allows the exploration of relationships among many different types of attributes. There are two types of multivariate analysis available: Classification (both Supervised and Unsupervised) and Principal Component Analysis (PCA).

The goal of classification is to assign each cell in a study area to a class or category. With Supervised classification, you have a specific knowledge about the study area and can identify representative areas, or samples, of each class. Unsupervised classification uses naturally occurring statistical groupings in the data to determine the clusters into which the data will be classified.

• Learn about multivariate classification
• Learn how to produce signature files and class and cluster analysis
• Learn how to evaluate classes and clusters
• Learn how to perform the classification

The general procedure for both Supervised and Unsupervised classification follows:

1. Identify the input bands.
2. Create the classes or clusters.

   The following tools can be used: Create Signatures, Iso Cluster, or Sample from the Extraction toolset.

3. Evaluate and edit the classes or clusters.

   Use the Dendrogram or Edit Signatures tools.

4. Perform the classification.

   Use the Maximum Likelihood Classification or Class Probability tools.

The Iso Cluster Unsupervised Classification tool allows you to conveniently perform an unsupervised classificaion by combining steps 1, 2, and 4 described above into a single tool.

The Image Classification toolbar provides an integrated environment to help with the multistep workflow that is necessary for performing a classification.

• Learn more about image classification

To eliminate redundancy in the data and make it more interpretable, you can transform your multivariate data through PCA.

• Learn more about transforming multivariate data with Principal Component Analysis (PCA)

The following table lists the available multivariate tools and provides a brief description of each.

Tools of the Multivariate toolset

Tool	Description
Band Collection Statistics	Calculates the statistics for a set of raster bands.
Class Probability	Creates a multiband raster of probability bands, with one band being created for each class represented in the input signature file.
Create Signatures	Creates an ASCII signature file of classes defined by input sample data and a set of raster bands.
Dendrogram	Constructs a tree diagram (dendrogram) showing attribute distances between sequentially merged classes in a signature file.
Edit Signatures	Edits and updates a signature file by merging, renumbering, and deleting class signatures.
Iso Cluster	Uses an isodata clustering algorithm to determine the characteristics of the natural groupings of cells in multidimensional attribute space and stores the results in an output ASCII signature file.
Iso Cluster Unsupervised Classification	Performs unsupervised classification on a series of input raster bands using the Iso Cluster and Maximum Likelihood Classification tools.
Maximum Likelihood Classification	Performs a maximum likelihood classification on a set of raster bands and creates a classified raster as output.
Principal Components	Performs Principal Component Analysis (PCA) on a set of raster bands and generates a single multiband raster as output.