The Grammer of Graphics 读书笔记 - Introduction

Grammar gives language rules.

Grammar makes language expressive.

1.1 Graphics Versus Charts

We often call graphics charts. For one thing, charts are usually instances of much more general objects.

Elegant design requires us to think about a theory of graphics, not charts.

The concept of a graphic is so general that we need organizing principles to create instances of graphics. We may not want to put a pie chart in a catalog, but we need to give users some simple way to produce one. For that, we need methodologies based on object-oriented design.

1.2 Object-Oriented Design

1.2.1 What is ODD?

• Objects are basic components of systems.

• Objects communicates with each other through simple messages.

• Objects are often reusable. They are relatively stupid.

• What objects do is encapsulated. Other objects have no idea how they work, and they don’t care.

• Components of OO systems are relatively modular.

• Objects can inherit attributes and behavior from other objects.

• Objects are often polymorphous.

1.2.2 What is NOT ODD?

• OOD is not a language.

• OOD is not a GUI.

• OOD is not an interactive system.

1.3 An Object-Oriented Graphics System

Three stages of graphic creation:

1. Specification

2. Assembly

3. Display

1.3.1 Specification

Specification involves the translation of user actions into a formal language. To represent data accurately and appropriately. consequently , the core of a graphics system must rest on specification.

Statistical graphic specifications are expressed in six statements:

1. DATA: a set of data operations that create variables from datasets,

2. TRANS: variable transformations(eg: ranks).

3. SCALE: scale transformations(eg: log).

4. COORD: a coordinate system(eg: polar).

5. ELEMENT: graphs (eg: points) and their aesthetic attributes(eg: color).

6. GUIDE: one or more guides (eg: axes, legends).

We separate the notation into components. These components link data to objects and specify a scene containing those objects.

1.3.2 Assembly

In order to portray a scene, we must coordinate its geometry, layout, and aesthetics in order to render it accurately. A statistical graphics computer program must be able to assemble a graphical scene from a specification in the same manner as a drawing or modeling program puts together a realistic scene from specification components. A scene can be dynamic, or static, linked to external data or isolated, modifiable or immutable, depending on how we assemble it.

1.3.3 Display

For us to perceive it, a graph must be rendered using aesthetic attributes and a display system.

1.3.3 Revision

By carefully separating the process of graph creation into hierarchical components, we enable a flexible environment that offers new views without recalculating every step in the system. And we can link controllers to any components or property in the system to provide direct manipulation of data, variables, frames, or rendering.