CHAPTER 1 Introduction

Overview

It is much easier to learn Freud by doing rather than reading. It is highly recommended that you try out some of the things you read about when you read about them.

Freud is based on objects. Each object in Freud represents a particular kind of plot. For instance, a map object is used to generate a background map. A contour object is used to generate a contour plot. An object is either a background object, or an overlay object. Background objects affect other objects; overlay objects exist independently of other objects. If, for example, you generate a map object (which is a background object), and then a contour object (which is an overlay object), the map object is used to generate the coordinate system used for plotting the contours described by the contour object. There are currently four objects in Freud-two background objects (map, xy) and two overlay objects (contours,vectors).

An object is a programming abstraction. It represents the Platonic ideal of the real object. If you want to do anything useful, you have to instantiate the object. An instantiation is the physical realization of an object. In Freud, an instantiation occurs when you click on an icon representing a particular object. Once this is done, you can physically manipulate this representation of an object. An object can have multiple instantiations. For instance, you can overlay several contour plots; each of the plots is described by an instantiation of the contour object.

• Type:

freud&

• Select Open from the File menu, or type control-O while the mouse is over the window that appeared when you typed the freud command.

• Load the file:

/usr/local/lib/freud/sample/gfdl_v830.mean.pkd

• (if you can't find this file, ask your system administrator where Freud's default library is located).

• Click the Accept button on the window that pops up after you load the file, and then click Cancel.

• Click on the Plot button in the main window. A (messy) contour plot will appear in the drawing area of the main window. Click on the button labeled Contour-0 to adjust contour values and attributes, or click on the button labeled Map-1 to change the appearance of the map.

User interface overview

The button can be activated by clicking on it. After you click on the button, something will happen; a new window might appear, or the appearance of the button might change.

Menus can have submenus. A submenu is indicated by an arrow to the right of the menu item. To view a submenu, first invoke the main menu by pressing and holding down MENU over an object with an attached menu; while continuing to hold down the mouse button, move the mouse until the item with the submenu is highlighted; slide the mouse to the right and the submenu will appear. An item on the submenu can be chosen by releasing the MENU button while the item is highlighted.

A menu item can also have an associated accelerator key. An accelerator key allows the user to access menu items without having to move from the keyboard to the mouse. An accelerator key is indicated by text on the right hand side of a given menu item; for instance, all windows (except the main window) can be closed by simultaneously pressing the control key and the c key; this is indicated by the text `Control+c' on the right hand side of the Close menu item.

There are two other buttons that commonly appear in the menu bar. The Edit button has an attached menu that allows you to change the state of an object. The Data button associates the data browser with a given object.

freud

If you don't want access to Freud's command line interface type:

freud &

The state of the entire application can be saved by choosing Defaults Save As from the File menu in the base window. Unlike earlier versions of Freud, you don't have to save the defaults for each instance before saving the global defaults.