Clear Filters
Clear Filters

Real quick one, passing through a matrix backwards or just flip it.

3 views (last 30 days)
During a for or while loop I would like to start at the back of the matrix and cycle to the beginning. Or do I just flip it using a(end:-1:1,:) or flipud(a). I understand flipud but can you briefly explain the syntax for a(end:-1:1,:).
Thanks AD

Accepted Answer

Fangjun Jiang
Fangjun Jiang on 27 Oct 2011
a=rand(8,9);
b=a(5:end,5:end)
"end" here is the length of that dimension.
1:end is the same as [1,2,3,...,end]
end:-1:1 is the opposite. It is the same as [end, end-1, end-2, end-3, ... 1].

More Answers (1)

Walter Roberson
Walter Roberson on 27 Oct 2011
Cycling the loop backwards
for K=size(A,1):-1:1
can be quite efficient, and seldom requires more memory than working forwards (indeed, moving forwards can be less efficient if you have not preallocated a matrix.)

Categories

Find more on Loops and Conditional Statements in Help Center and File Exchange

Tags

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!