MATLAB Workshop 6 | Study notes Matlab skills

MATLAB: Workshop 6 - Scripts and the Workspace page 1

MATLAB Workshop 6 - Scripts and the Workspace

Objectives: Learn about how MATLAB scripts interact with the workspace.

• Scripts and the Workspace

An understanding of how the scripts that you are learning to create for MATLAB interact with

the MATLAB workspace is critical for control of your workspace and debugging your scripts.

Frequently, scripts will have errors when first created. The process of removing the errors so that the

scripts work properly and provide correct answers is called debugging.

This workshop requires that MATLAB scripts named wkshp6_ac1.m, wkshp6_ac3.m, and

wkshp6_ac4.m be in the current directory. These scripts are available on the program disk. Please

copy them into the current MATLAB directory before proceeding.

(1) Scripts put their variables in the workspace.

Whenever a script is run, all variables that have values assigned are placed into the

workspace. To clearly see this, start with a clear workspace. Enter

» clear all

to completely clear the workspace. Check that this has been done by entering

» who

No variables should be listed in response. Now run wkshp6_ac1 by entering

» wkshp6_ac1

Workshop 6, Activities 1 and 2

Please provide diary name ==>

The script header and a request for a diary name appear. This particular script allows you

to provide a diary name that will hold the contents of running the script. You can look at

the script file later to see how this is done. Of interest is that you can use a script to turn

the diary on and off. Enter a diary name of your choosing and press enter. The MATLAB

command prompt appears. This means that the script has run!! Yet nothing appeared in

the Command Window. So what did happen? Enter

» who

Your variables are:

diary_name x y z

Running the MATLAB script has put variables into your workspace. If you want, you can

check to see what the variable types are (whos) and what values they contain. You might

also want to check on whether the diary file has been placed in the current directory.

(2) Scripts will overwrite existing values for variables of the same name in the workspace.

Scripts use the active workspace in the same manner that you do when you operate from

the command window. Any command issued in a script is the same as if you used the

command directly. Sometimes unexpected results occur. One is that scripts will replace

values for variables with the same name with their own values. To see this, enter the

following

» clear all

»x=7

• Running a MATLAB script will add all of the script variables to the active workspace.

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MATLAB Workshop 6 - Scripts and the Workspace

Objectives : Learn about how MATLAB scripts interact with the workspace.

• Scripts and the Workspace

An understanding of how the scripts that you are learning to create for MATLAB interact with

the MATLAB workspace is critical for control of your workspace and debugging your scripts.

Frequently, scripts will have errors when first created. The process of removing the errors so that the

scripts work properly and provide correct answers is called debugging.

This workshop requires that MATLAB scripts named wkshp6_ac1.m, wkshp6_ac3.m, and

wkshp6_ac4.m be in the current directory. These scripts are available on the program disk. Please

copy them into the current MATLAB directory before proceeding.

(1) Scripts put their variables in the workspace.

Whenever a script is run, all variables that have values assigned are placed into the workspace. To clearly see this, start with a clear workspace. Enter » clear all to completely clear the workspace. Check that this has been done by entering » who » No variables should be listed in response. Now run wkshp6_ac1 by entering » wkshp6_ac Workshop 6, Activities 1 and 2 Please provide diary name ==> The script header and a request for a diary name appear. This particular script allows you to provide a diary name that will hold the contents of running the script. You can look at the script file later to see how this is done. Of interest is that you can use a script to turn the diary on and off. Enter a diary name of your choosing and press enter. The MATLAB command prompt appears. This means that the script has run!! Yet nothing appeared in the Command Window. So what did happen? Enter » who Your variables are: diary_name x y z Running the MATLAB script has put variables into your workspace. If you want, you can check to see what the variable types are (whos) and what values they contain. You might also want to check on whether the diary file has been placed in the current directory.

(2) Scripts will overwrite existing values for variables of the same name in the workspace.

Scripts use the active workspace in the same manner that you do when you operate from the command window. Any command issued in a script is the same as if you used the command directly. Sometimes unexpected results occur. One is that scripts will replace values for variables with the same name with their own values. To see this, enter the following » clear all » x = 7

Running a MATLAB script will add all of the script variables to the active workspace.

x = 7 » who Your variables are: x to completely clear the workspace and then introduce the variable x with the value 7.

Now run wkshp6_ac1 again by entering » wkshp6_ac Workshop 6, Activities 1 and 2 Please provide diary name ==> Respond with a diary name of your choice and enter » who Your variables are: diary_name x y z The script again added its own variables. Check on the value for x. Enter » x x = 1 Running the MATLAB script changed the value of x from 7 to 1. This can be dangerous because there is no warning that the script was using a variable name the same as one you already had in the workspace.

(3) Scripts will use existing variables of the same name in the workspace.

This issue is important in designing and debugging scripts. A common method for developing scripts is to work a sample problem with the diary on and then edit the diary to create a script. This is the method illustrated in Workshop 5. However, there is a problem with this approach in that the workspace contains the variables that were used to develop the script (same names). Improper editing of the diary file to create the script can result in a situation such as the following. Enter » clear all » x = 1; » y = 2; » z = 3; » wkshp6_ac Workshop 6, Activity 3 Please provide diary name ==> Respond with a diary name of your choice and press enter. The command prompt appears, indicating that the script has executed without any problems.

Now try (provide a diary name of your choice when requested) » clear all » wkshp6_ac Workshop 6, Activity 3 Please provide diary name ==> ??? Undefined function or variable 'x'. Error in ==> c:\temp\wkshp6_ac3.m On line 23 ==> d = x*y;

Running a MATLAB script will change the values assigned to variables with the same name.
- Avoid this by using unique variable names in your scripts.

MATLAB Workshop 6, Study notes of Matlab skills

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Download MATLAB Workshop 6 and more Study notes Matlab skills in PDF only on Docsity!

MATLAB Workshop 6 - Scripts and the Workspace

Objectives : Learn about how MATLAB scripts interact with the workspace.

• Scripts and the Workspace

An understanding of how the scripts that you are learning to create for MATLAB interact with

the MATLAB workspace is critical for control of your workspace and debugging your scripts.

Frequently, scripts will have errors when first created. The process of removing the errors so that the

scripts work properly and provide correct answers is called debugging.

This workshop requires that MATLAB scripts named wkshp6_ac1.m, wkshp6_ac3.m, and

wkshp6_ac4.m be in the current directory. These scripts are available on the program disk. Please

copy them into the current MATLAB directory before proceeding.