Executing loop on certain numbers

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Raghavendra Reddy P
评论： Raghavendra Reddy P 2015-5-11
i have two vectors L=1:12; idx=[3 5 9]; I wanted to execute for loop for i=12:-1:1 now i want execute vector idx, starting from last elemet to first i.e 9,5,3 something like
if i==9
do stuff
end
if i==5
do stuff
end
.
.
if i==3
do stuff
end
end
i don't know how many elements in vector idx before hand.

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Stephen23
Stephen23 2015-5-11
编辑：Stephen23 2015-5-11
You can execute over the vector backwards by using basic MATLAB indexing:
idx = [3,5,9];
for k = idx(end:-1:1)
... code here
end
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Stephen23
Stephen23 2015-5-11
编辑：Stephen23 2015-5-11
For a start you could use switch inside the loop:
for k = idx(end:-1:1)
switch k
case 9
... code
case 5
... code
case 3
... code
otherwise
error('This values is not known: %d',k)
end
end
But, depending on what those calculations are, there might be much easier and faster ways of achieving this. If you tell us exactly what the do stuff operations actually are, then we might be able to tidy this up too. Can the the vector idx change, or is it always the same?
Raghavendra Reddy P
Raghavendra Reddy P 2015-5-11
Thank you sir, soon i will write what calculations and stuff to do. vector idx will change.

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