Курсовая работа_ф_3 / FreematPrimerV4e1

Topic 1.1.3: The Variables Section

The variables section shows all of the current global variables. If you worked with Freemat Ver. 3.6, this was found under the "Workspace" tab. Now it's under its own section. It will also show the variables used in a function so long as the function is operating. Frankly, I use this window perhaps more than any of the others. It gives me a quick preview of the variables being used, especially if I'm troubleshooting a script or function.

Figure 6: The Variables Section

Topic 1.1.4: The Debug Section

The "Debug" section shows any errors or warnings that Freemat provides. Typically, the first part of the line will be the time at which it occurred, followed by the text of the error or warning itself.

See Figure 7. I mainly use this to identify when something goes wrong with a function or script I'm running.

Figure 7: The Debug Section.

Topic 1.1.5: The Working Directory

The working directory is nothing more than the default folder into which Freemat reads data files from and saves files to, unless a different folder is specified in

the specific input or output operation. For example, if Figure 8: The Working Directory. you use the print function to store an image, it will go

into this directory unless you explicitly specify a different directory within the function. As well as from the small window at the top of the Freemat

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Caution - File Outputs for Windows Vista and Windows 7 Users

When Freemat is installed in either Windows Vista or Windows 7, the default working directory is made the Freemat folder within the Program Files directory (C:/Program Files/Freemat). Since WinVista and Win7 protect all files within the Program Files directory, as well as all sub-folders, Freemat will not be able to save any data to this directory or any of its sub-folders. And you thought that that funny "Cancel or Allow" Mac commercial was just being sarcastic? No. They were serious. This is due to the enhanced security Microsoft has built into these operating systems. It restricts which programs are allowed to manipulate the core operating files. Unfortunately, neither Freemat nor Vista / Win7 will provide any indication that the save / store operation did not work. I found this out the hard way while running some scripts on my Vista-based laptop. After running the scripts in which I expected to see saved data, I checked in the Program Files/Freemat folder and found... my data was not there. Please learn from my lesson. If you're using Freemat within Vista or Windows 7, change your working directory to some folder within your "User" folder. You'll be very glad you did!

Topic 1.2.1: Setting the Working Directory Using the cd Command

The working directory is nothing more than the default folder into which Freemat reads data files from and saves files to, unless a different folder is specified in the specific input or output operation.

The working directory is nothing more than the default folder from which Freemat reads data files and to which it saves files.

Example - Changing the Working Directory using the cd Command

The cd command changes the working directory to which directory is specified in the command.

Here's an example from a Linux (Ubuntu) system.

--> pwd ans = /home/gary

--> cd '/home/gary/Freemat/' --> pwd

ans = /home/gary/Freemat

Here's an example from a Windows XP system.

--> pwd ans =

C:/Program Files/FreeMat

--> cd 'C:/Documents and Settings/Owner/My Documents'

--> pwd ans =

C:/Documents and Settings/Owner/My Documents

One thing to note. Typically, a Linux system uses a forward slash (/), whereas Windows systems sometimes use a forward slash (/) and sometimes use a back slash (\). In a Windows version of

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Freemat, whether XP, Vista or Win7, it doesn't matter whether you use a forward slash (/) or a back slash (\) to separate the different directories. Freemat will change them to whatever it wants. In the Linux version, however, you must use a forward slash; otherwise, Freemat will return an error.

We'll cover scripts and functions in a later section. A script is nothing more than a set of commands listed in a text file (with the difference that it has a ".m" suffix). Freemat will run them one at a time. going from top to bottom, until it reaches the end. If there is a script called startup.m anywhere in the path for Freemat, it will run it each time that Freemat is started. Therefore, one way to set the working directory is to create a script called startup.m and use it to change the working directory using the cd command.

By default (for Windows users), the working directory is C:/Program Files/Freemat x, where x is replaced by whatever version of Freemat you first installed. And x may be different than what you are currently using. That's because Freemat may not change the directory name if you've upgraded. (It did not change for me when I upgraded Freemat on my WinVista machine from 3.5 to 3.6. It did change on my WinXP system.) By default, Freemat will attempt to save all of your data to your working directory. Okay, this is not that big a deal when saving scripts because Windows uses a standard "Save File" window that explicitly makes you choose a folder. But for your data reads (such as the fread, wavread or dlmread commands) and writes (such as the wavwrite or print commands), you should take heed and change the working directory to something other than the Program Files directory.

Example - Setting the Default Working Directory in a Windows System

After installing Freemat in a Windows system, you'll really want to change the default working directory. Changing the working directory such that it's set automatically when Freemat starts up is a three-step process. The steps are:

1.Create a new folder for your Freemat files in your "Users" directory (if you're running Win7 or WinVista), your "My Documents" directory (if you're running WinXP), or your home directory (if you're running Linux).

2.Add this new folder to your path list in Freemat.

3.Create a script called startup.m containing a cd command pointing to this new Freemat file. The first step should be familar to anyone using a PC. Go into your personal directory, which is:

• "C:\Documents and Settings\<user name>" in a Windows XP system.

• "C:\Users\<user name>" in a Windows Vista or Windows 7 system.

Some examples of these are shown in Figure 9 and Figure 10.

Figure 9: Windows Explorer showing Address Bar in a Windows XP system.

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Figure 11: Path Tool window showing selection of newly-created folder under user directory.

The final step is to create a script called startup.m and place it in this folder. Here's a quick overview of the steps involved:

1.Open the Freemat Editor. To do so, type "edit" in the command section followed by pressing the <Enter> key or select Tools -> Editor from the Freemat menu.

2.In the editor window, type a cd (change directory) command (FD, p. 415) followed by the full path name of the folder you just created. Here are examples of the commands based on some different operating systems. You can also see an example, for a Windows 7 system, in Figure 12.

(a)Windows XP: cd 'C:\Documents and Settings\Owner\My Documents\Freemat';

(b)Windows Vista \ Windows 7: cd 'C:\Users\Owner\Documents\Freemat';

3.In the Editor window, click on File -> Save, navigate to the folder listed in the cd command, give it the name startup.m (This particular filename is important! Don't call it anything else!), and press "Save".

4.Exit the Editor window.

Now test your new script. Exit out of Freemat and re-start it. If the working directory is now listed as this new folder under your personal directory, then success! For now, anything you save from Freemat will be stored in this directory by default (again, unless you specifically say otherwise in whatever command is used to save the file).

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Figure 12: Freemat Editor window with cd command that changes the working directory to a folder under the user's personal directory. This is a Windows 7 system.

Example - Saving a File to the Working Directory

This is from the Freemat v4.0 Documentation. This example is being run on a Linux-version of

Freemat. First, here's the current working directory:

--> pwd /home/gary/Freemat

Here's a short set of commands that generates a set of random numbers, then writes them to a file called "test.dat". Since the path to the file is not explicitly stated, it's written to the working directory. In this

case, it's "/home/gary/Freemat".

--> A=float(randn(512));

--> fp=fopen('test.dat','w');

--> fwrite(fp,A,'single'); --> fclose(fp);

This creates and opens a file called "test.dat" and makes it writable (the 'w' property in the fopen command). Since the path to the file is not specified, it's placed into the working directory.

Here's an example from a Windows 7 system showing how the operating system denies Freemat the ability to write to the default working directory (the C:Program Files (x86)/Freemat directory, to be

specific).

--> pwd ans =

C:/Program Files (x86)/Freemat

--> A=float(randn(512));

--> fp=fopen('test.dat','w');

Error: Access is denied. for fopen argument test.dat -->

This error occurs because Win7 (and WinVista) prevent a user from making changes to the core files (such as are found in the Program Files directory). Both Win7 and WinVista require going through its

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