# Data Matrix

The data matrix is HUGINs tool for inspecting and manipulating data sets. Data is displayed using a grid like interface very similar to what most users know from Excel, see Figure 1. The data matrix is available in places dealing with data files, including the learning- and EM wizards, the data frame functionallity and other places dealing with data.

Figure 1: A typical data matrix view

The leftmost column is the row header which display row numbers, first row is 0 as rows are zero-indexed. The top header display column names, when using data with a HUGIN model the columns represent nodes.

## Basic Editing

The data set can be inspected using the data matrix. Although HUGIN is not EXCEL, some basic editing of data items can be performed:

- Use Mouse pointer or cursor-keys to navigate about

- Double-click a cell to edit the data item (see Figure 2)

Figure 2: Editing a cell

- Double-click column header to edit column name (see Figure 3)

Figure 3: Renaming column

- Search and replace values in single column/all columns by right-clicking and selecting Replace values (see Figure 4)

Figure 4: Basic search and replace

- Re-order columns by clicking a column header and dragging the column left or right

- An entire column can be filled with a single value by right-clicking and selecting Fill with value (see Figure 5)

Figure 5: Fill column with values

Rows and columns can be edited as well:

- Create/delete row by right-clicking row header and selecting insert- or delete row

- Create/delete column by right-clicking column header and selecting insert- or delete column

Figures 6 and 7 display the options available by right-clicking row header and column.

Figure 6: Right-click the row header - options

Figure 7: Right-click column - options

## Advanced Functionallity

Columns containing numerical data, exclusively, can be discretized into a set of intervals by launching the discretizer (read more about the discretization features):

- Right-click a column containing numerical data and select Discretize values

More elaborate modifications are performed using batch preprocessing (read more about the preprocessing (Data Processing) features):

- Right-click and select the Data Processing option

To inspect properties of the data set use the data set analysis functionallity (read more about the data analysis features):

- Right-click and select the Analysis option

It is also possible to plot a single column’s data against the row ID’s

- Right-click and select the Plot column option

To perform analysis of classifier performance (read more about the classifier performance analysis):

- Right-click and select the Classifier Performance option