For loop with if and elseif statements

Could someone please help me out?

I've been writting a code for some time now, and I endend up having quite a big matrix for loop with many statements. Now I want to modify that loop and some of it's statements, but I came up with some issues. First of all, I'd like to know if I coud write a new statement where I could ask the program to skip some iterations within the loop until a certain position on my matrix. For example, let's say I have an Input A(m,n) such as:

A = [2 0.5 1 2 0 -1 0 -1 6 4 3 0 ; 0 3 4 0.5 6 0 0 -1 0 0 -1 0];

What I expect from the code is to add the value of each position to the addition of the previous ones, except when the value is 0.5, that I'd like to hold the value until you come up with a -1, where I'd like to multiplyit by 2.

Expected Output:

Out = [2 2 2 2 2 4 4 8 14 18 21 21; 0 3 7 7 7 7 7 14 14 14 24 24]

Any help with this? Also, would it be interesting changing this part of the code from is and elseif statements to a switch case structure?

Thank's for the help,

Santos

Answer 1

[Matt J]

You can use continue

https://www.mathworks.com/help/matlab/ref/continue.html

[Santos García Rosado]

Thank's for your quick answer Matt. I read the documentation about the continue function and also tried to use it practically on my code.

However I can't figure out how to make it continue to a certain point (in this case -1). It only skips until the following iteration. Could you please give me a hand?

Thank you

AAA = [0 0.5 1 2 0 -1 0 -1 6 4 3 0 ; 0 3 4 0.5 6 0 0 -1 0 0 -1 0];
BBB = zeros(size(AAA));
BBB(1,:) = AAA(1,:);
for f = 1:size(AAA,1)
    for c = 2:size(AAA,2)
        if AAA(f,c) == 0.5
            BBB(f,c) = BBB(f,c-1);
            continue
        elseif AAA(f,c) == -1
            BBB(f,c) = BBB(f,c-1) * 2;
        else
            BBB(f,c) = BBB(f,c-1) + AAA(f,c);
        end
    end
end

[Matt J]

Perhaps as follows.

AAA = [0 0.5 1 2 0 -1 0 -1 6 4 3 0 ; 0 3 4 0.5 6 0 0 -1 0 0 -1 0];
BBB = zeros(size(AAA));
BBB(1,:) = AAA(1,:);

holdState=0;

for f = 1:size(AAA,1)
    for c = 2:size(AAA,2)
        
        if AAA(f,c) == 0.5 || holdState
            
            BBB(f,c) = BBB(f,c-1);
            
            if AAA(f,c) == 0.5, holdState=1; end

        elseif AAA(f,c) == -1
            
            BBB(f,c) = BBB(f,c-1) * 2;
            holdState=0;
            
        else
            
            BBB(f,c) = BBB(f,c-1) + AAA(f,c);
            
        end
        
    end
end

[Santos García Rosado]

Hi Matt. Thank's again for the feed back, but it's still not working. I've been trying to use your code, but output BBB is a zero(2x12) matrix. I've been trying to work a solution around your answer but still couldn't find a way.

[Matt J]

This seems to work

AAA = [0 0.5 1 2 0 -1 0 -1 6 4 3 0 ; 0 3 4 0.5 6 0 0 -1 0 0 -1 0];
BBB = zeros(size(AAA));
BBB(1,:) = AAA(1,:);



for f = 1:size(AAA,1)
    
    holdState=0;
    
    for c = 2:size(AAA,2)
        
        if AAA(f,c) == 0.5 || holdState
            
            BBB(f,c) = BBB(f,c-1);
            
            if AAA(f,c) == 0.5, holdState=1; end

        elseif AAA(f,c) == -1
            
            BBB(f,c) = BBB(f,c-1) * 2;
            holdState=0;
            
        else
            
            BBB(f,c) = BBB(f,c-1) + AAA(f,c);
            
        end
        
    end
end

BBB

BBB = 2×12

0 0 0 0 0 0 0 0 0 0 0 0 0 3 7 7 7 7 7 7 7 7 7 7

[Santos García Rosado]

It seems like te holdState variable is not making stop the skipping iteration at AAA = -1, but it is holding that value until the end of each row. For Input:

AAA = [0 0.5 1 2 0 -1 0 -1 6 4 3 0 ; 0 3 4 0.5 6 0 0 -1 0 0 -1 0];

The Output should look like:

BBB = [0 0 0 0 0 0 0 0 6 10 13 13; 0 3 7 7 7 7 7 14 14 14 28 28]

[Matt J]

AAA = [0 0.5 1 2 0 -1 0 -1 6 4 3 0 ; 0 3 4 0.5 6 0 0 -1 0 0 -1 0];
BBB = zeros(size(AAA));
% BBB(1,:) = AAA(1,:);



for f = 1:size(AAA,1)
    
    holdState=0;
    
    for c = 2:size(AAA,2)
        
        if AAA(f,c) == 0.5 || (holdState && AAA(f,c)~=-1)
            
            BBB(f,c) = BBB(f,c-1);
            
            if AAA(f,c) == 0.5, holdState=1; end

        elseif AAA(f,c) == -1
            
            BBB(f,c) = BBB(f,c-1) * 2;
            holdState=0;
            
        else
            
            BBB(f,c) = BBB(f,c-1) + AAA(f,c);
            
        end
        
    end
end

BBB

BBB = 2×12

0 0 0 0 0 0 0 0 6 10 13 13 0 3 7 7 7 7 7 14 14 14 28 28

[Santos García Rosado]

That solved it! Thank's for your time Matt!