What is wrong with this for loop command in MATLAB (excluding an index)

I am trying to exclude an index within a for loop. I can't understand why the following code keeps bringing up an error:

for

for(l=1:Nmax, l~=m)


The error is

Error: File: BARW2Dwithducts.m Line: 76 Column: 24
Unbalanced or unexpected parenthesis or bracket.

I don't see how the expression is unbalanced (the code itself works fine and is error free if I just use for l=1:Nmax, but this doesn't give me what I need...

for l=1:Nmax

The error is trying to tell you your syntax is incorrect. To skip you would have to check the value inside the for loop with an if statement
– scrappedcola
Jun 29 at 17:32

Where did you see this syntax? You can’t just make up new syntax and expect it to work. Please read the MATLAB documentation page on the for loop. If the syntax is not described there, it’s not legal syntax.
– Cris Luengo
Jun 29 at 17:40

2 Answers
2

To skip an index, your typical option is to put the following inside the loop (as the first thing):

if (l == m)
continue
end


Another option is to generate all indices, then remove the target one:

allInds = 1:Nmax;
allInds(allInds == m) = ; % remove index m.
for l = allInds
...


This has a nice advantage that you can clearly see all the indices that will be visited before the loop even starts, and as you start adding extra conditions this one scales much better than a horrible nest of conditions inside the loop.

One way to skip the value m is to do as follows:

m

for l=[1:m-1,m+1:Nmax]
% ...
end


Note that this will not work if m-1>Nmax, as you will visit values larger than Nmax.

m-1>Nmax

Nmax

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