# Channels

Channels are the visual encoding for data attributes.

There are various types of channels, including:

* position
* size (length, width, area)
* angle and slope
* color (intensity and hue)
* shape and texture

## Position

Position is one of the most commonly used channels. Almost every visualization uses position.

For example, in a scatter plot, the position of a point denotes the values of two attributes.

In bar charts, the position of a bar identifies a category.

In a network diagram, the positions of the nodes and links is also meaningful.

## Size

Size can be 1D (length and width) or 2D (area).

In a bar chart, the length of a bar denotes a quantity.

In a line chart or a network diagram, the width of a line may denote a quantity.

In scatter plots and symbol maps, the areas of the symbols denote quantities.

## Angle and Slope

In a line chart, if the x-axis denotes time, the slope of the line denotes the **rate of change** of a quantity.

In pie charts, the angles denote **proportions** associated with the values in he corresponding segments.

## Color

Color is not a single channel; it is actually 3 channels. Here, we discuss 2 channels: hue and intensity.

**Hue** is the name of the color i.e. red, green, blue etc. It is used to encode *categorical* information.

**Intensity** refers to the brightness of a color. It is used to encode *quantitative* information. (In other terms, **luminance** is the amount of light emitted by a color and **saturation** is the vividness of the color).

## Shape and Texture

In a scatter plot, different categorical data items can be identified using different shapes.

In a bar chart, bars can be given different textures, to identify different categories.