将多个IF语句组合成一个（matlab）？

Question

Would there be a way to combine several if statements to perform in the same sequence as below:

X = [1 2 3 4; 5 4 6 7; 2 8 9 2];
X

n = length(X(1,:))-1;

for i=1:n,     
    if length(X(1,:)) == n,
    .........
    end

    if length(X(1,:)) == n-1,
    .........
    end

    if length(X(1,:)) == n-2,
    .........
    end
end

Any suggestions?

Answer 1

Judging from the code you provide, and the comment you gave Theodros, I think this is a case of code smell . In other words, I have a hunch there are deeper problems with your approach, which we might be able to improve upon if you disclose your full problem.

Now, having said that: if the operations you want to perform differ for each case, then obviously, you can't combine them into one statement. If there are multple copies of the same procedures in each block, you can use logical OR:

if length(X(1,:)) == n || length(X(1,:)) == n-1
    ...
end

if length(X(1,:)) == n-2 || length(X(1,:)) == n-4
    ...
end

The code will look nicer (and be slightly faster) if you use the switch statement, as @TheodrosZelleke suggested. Combining cases goes like this:

switch length(X(1,:))

    case {1 2}  %# length == 1 OR length == 2
        ...
    case {3 4}  %# length == 3 OR length == 4
        ...
end