Notes 01: Introduction to MATLAB

Components of MATLAB's Desktop

• Command Window
  This is the primary interface for MATLAB's interpreter. It is where commands are entered in order to be executed. With octave, this is the only component.

• Command History
  This provides a history of all commands that were entered into the Command Window, including from previous sessions. You may click/drag past commands to re-execute them in the Command Window. It is also possible to revisit past commands directly at the Command Window prompt by using the up/down arrows.

• Workspace
  This provides a view of all currently defined variables during a MATLAB session. For each variable it can display the name, the data class, the array size, and the values. It is also possible to edit an existing variable graphically by double clicking on its name, invoking the spreadsheet-like Variable Editor.

• Current Directory
  Script and function m-files from the current directory can be used directly from the command window. The current directory is also relevant when saving and loading data.

Managing the Workspace

• x = value;
  assigns the variable name x to whatever value is expressed on the righthand side of the assignment operator (=). If x had previously been defined, this assignment reassigns the name to the new value.

  If an expression is ever entered without an explicit assignment, the result will automatically be assigned the the variable ans.

  By default, the result of each command is automatically echoed by MATLAB. To avoid that output, a command must be followed by a semicolon (;).

• who
  lists the names of all variables currently defined in the workspace.

• whos
  lists the names and associated data for all variables currently defined in the workspace.

• clear x
  removes the variable x from the current workspace.

• clear
  clears the workspace of all previously defined variables.

• clc
  visibly clears the command window (but leaves the underlying workspace unchanged).

• disp(x)
  displays the value of x (but without displaying the variable name).

• help x
  prints informational text about x in the command window.

• doc x
  brings up the MATLAB documentation viewer with (typically) more extensive information about topic x.

Creating and using an "m-file"

While the interactive Command Window is convenient, we do not always want to restart from scratch or to have to retype a long series of commands. We can save a series of commands in a text file that is traditionally known as an "m-file" in MATLAB lingo (because it is saved using a filename such as myproject.m).

The percent sign is used in MATLAB to designate the remainder of any line as a comment. This provides a convenient way for documenting portions of your source code. For example, you might write

gravity = 9.8;       % measured in meters/second^2