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How do I comment out a large block of code in MATLAB?

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I want to do this in an easy way.

Accepted Answer

Doug Hull
Doug Hull on 29 Aug 2023
Edited: MathWorks Support Team on 29 Aug 2023
To comment out a large block of code in the Editor or Live Editor, select the code and on the "Editor" or "Live Editor" tab, click the "Comment" button. This inserts a "%" symbol in front of each selected line. Alternatively, select the code and type "Ctrl" + "R". To uncomment the selected text, click the "Uncomment" button or type "Ctrl" + "Shift" + “R”.  
On macOS systems, use “Command” + “/” to comment and “Command” + “Option” + “/” to uncomment. On Linux® systems, use “Ctrl” +”/” to comment and “Ctrl” + “Shift” + “/” to uncomment. 
You also can use the block comment operators "%{" and "%}". The "%{" and "%}" operators must appear alone on the lines that immediately precede and follow the block of help text. For example: 
     code to be commented out 
Steven Lord
Steven Lord on 12 Mar 2021
That functionality is still present in releases R2020a, R2020b, and R2021a. It is possible that something about your file or how you're writing these comment delimiters is preventing them from being interpreted as block comments. For instance, %{ and %} must appear alone on a line.
x = 1
x = 1
%{ start of block comment?
y = 2
y = 2
z = 3
z = 3
w = 4
v = 5
Because of the text following the %{ before "y = 2" it is a regular comment, not a block comment. So we execute the line that creates the y variable.
Because there is no %{ associated with the %} before "z = 3" it too is a regular comment and the z variable is created.
The %{ and %} surrounding the lines defining the w and v do comprise a block comment, so those variables are not created.
Name Size Bytes Class Attributes x 1x1 8 double y 1x1 8 double z 1x1 8 double
Can you show us a small code segment where you see %{ and %} not functioning as block comments?
Shapol Mohamed
Shapol Mohamed on 18 Mar 2021
In Matlab 2020, you have to use ctrl+/ (cmd+/ for mac) to comment a block and to uncomment you have to use ctrl+t (cmd+t for mac).

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More Answers (3)

Ctrl + R comment selected lines. Ctrl + T uncomment select lines.
Steven Lord
Steven Lord on 15 Jun 2023
Search the list of keyboard shortcuts for the word "comment" or for the key combination Ctrl+T and you should see the actions associated with commenting out code or that will be performed in various components of the MATLAB Desktop in the keyboard shortcut set you've told MATLAB to use.
In my MATLAB installation using the Windows keyboard shortcut set, Ctrl+T creates a new tab in the Help Browser but uncomments code when used in the Editor.

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Wesam Rezk
Wesam Rezk on 30 Mar 2018
Simply start with *... and write whatever you want. This will enable you to write a very long comment line
For example *... This is a very very long comment

Wick on 1 May 2018
Edited: Wick on 1 May 2018
Rather than comment large sections of code, I bypass them with the following syntax.
for dont_go_here = []
% code I want to skip including all nested comments, etc. can stay here unmolested
This assumes that your if, for, case, try, and switch commands within that block are all terminated properly with an 'end' Otherwise the script won't parse.


Find more on Entering Commands in Help Center and File Exchange


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