MATLAB 5.0 Enhancements (Upgrading from MATLAB 4 to MATLAB 5.0)

Upgrading from MATLAB 4 to MATLAB 5.0

Programming Capabilities

MATLAB 5.0 included flow-control improvements and new M-file programming tools.

Flow-Control Improvements

MATLAB 5.0 featured:

A new flow-control statement, the switch statement
More efficient evaluation of if expressions

The switch statement is a convenient way to execute code conditionally when you have many possible cases to choose from. It is no longer necessary to use a series of elseif statements:

switch input_num
    case -1
        disp('negative one');
    case 0
        disp('zero');
    case 1
        disp('positive one');
    otherwise
         disp('other value');
end

Only the first matching case is executed.

switch can handle multiple conditions in a single case statement by enclosing the case expression in a cell array. For example, assume method exists as a string variable:

switch lower(method)
    case {'linear','bilinear'}, disp('Method is linear')
    case 'cubic', disp('Method is cubic')
    case 'nearest', disp('Method is nearest')
    otherwise, disp('Unknown method.')
end

**Table 1-6: New Flow Control Commands**
Command	Description
`case`	Case switch.
`otherwise`	Default part of `switch` statement.
`switch`	Conditionally execute code, switching among several cases.

MATLAB now evaluates if expressions more efficiently than before. For example, consider the expression if a|b. If a is true, then MATLAB will not evaluate b. Similarly, MATLAB won't execute statements following the expression if a&b in the event a is found to be false.

**Table 1-7: New Logical Operators**
Operator	Description
`iscell`	True for a cell array.
`isequal`	True if arrays are equal.
`isfinite`	True for finite elements.
`islogical`	True for logical arrays.
`isnumeric`	True if input is a numeric array.
`isstruct`	True for a structure.
`logical`	Convert numeric values to logical vectors.

M-File Programming Tools

MATLAB 5.0 added four features to enhance MATLAB's M-file programming capabilities.

Variable Number of Input and Output Arguments

The varargin and varargout commands simplify the task of passing data into and out of M-file functions. For instance, the statement function varargout = myfun(A,B) allows M-file myfun to return an arbitrary number of output arguments, while the statement function [C,D] = myfun(varargin) allows it to accept an arbitrary number of input arguments.

Multiple Functions Within an M-File

It is now possible to have subfunctions within the body of an M-file. These are functions that the primary function in the file can access but that are otherwise invisible.

M-File Profiler

This utility lets you debug and optimize M-files by tracking cumulative execution time for each line of code. Whenever the specified M-file executes, the profiler counts how many time intervals each line uses.

Pseudocode M-Files

The pcode command saves a pseudocode version of a function or script to disk for later sessions. This pseudocode version is ready-to-use code that MATLAB can access whenever you invoke the function.

**Table 1-8: New Programming Tools**
Function	Description
`addpath`	Append directory to MATLAB's search path.
`assignin`	Assign variable in workspace.
`edit`	Edit an M-file.
`editpath`	Modify current search path.
`evalin`	Evaluate variable in workspace.
`fullfile`	Build full filename from parts.
`inmem`	Return functions in memory.
`inputname`	Return input argument name.
`mfilename`	Return name of the currently running M-file.
`mexext`	Return the MEX filename extension.
`pcode`	Create pseudocode file (P-file).
`profile`	Measure and display M-file execution profiles.
`rmpath`	Remove directories from MATLAB's search path.
`varargin, varargout`	Pass or return variable numbers of arguments.
`warning`	Display warning message.
`web`	Point Web browser at file or Web site.

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