set order of elseif

Updated.

I have this code structure inside a loop. x, y and z are 1/0 variables. In this case the order of the elseif statement is: first x is evaluated, then y then z

if x  
    %code for case x    
elseif y
    %code for case y
elseif z 
    %code for case z    
end

I would like to define a varible order (for the previous case order={'caseX','caseY','caseZ'}), where I can change the order in which the elseif statement is evaluated. So if I set order={'caseZ','caseX','caseY'}, I should get this: (first z is evaluated, then x then y)

order={'caseZ','caseX','caseY'}

%%% then 

if z  
    %code for case z    
elseif x
    %code for case x
elseif y 
    %code for case y    
end

An hint will be appreciated.

[Ive J]

I'm not sure if I understood you correctly, but seems easier if you use switch/case. See here:

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

[KSSV]

Have a look on switch.

Answer 1

[James Tursa]

Does this do what you want:

order = [1 2 3]; % or whatever
for k=1:numel(order)
    switch order(k)
    case 1
        if( x )
            % code for case x
            break;
        end
    case 2
        if( y )
            % code for case y
            break;
        end
    case 3
        if( z )
            % code for case z
            break;
        end
end
   

Or if you prefer the case selection could be for characters 'x', 'y', and 'z' instead of numbers 1, 2, 3.

The key is to have those break statements inside the cases so that the if-elseif-elseif control structure is emulated properly.

[Rub Ron]

so, the if-elseif-elseif is replaced by a for-switch-if . Any idea if this replacement is computationaly expensive? Those lines are executed hundred or thousands of times.

[James Tursa]

Probably the only way to see the difference is to code it both ways (i.e., a hard-coded order vs the above logic) and use the profiler.

[Rub Ron]

At the end I combine your answer with Bruno's:

b = [x y z]; % logical conditions (in if/elseif)
[~,i] = ismember(prefered_order, {'x','y','z'});
j = find(b(i), 1, 'first');

switch prefered_order(j)
    case 'x'
        % code for case x   
    case 'y'
        % code for case y    
    case 'z'
        % code for case z
end

[James Tursa]

How can this work for you? I don't see any looping that will emulate the if-elseif-elseif control structure.

[Rub Ron]

in this case a loop is not needed. The key is in:

j = find(b(i), 1, 'first');

consider:

prefered_order = {'z','x','y'}

[James Tursa]

Ah, yes, I missed that ...

[Bruno Luong]

I like the combo solution.

[Rub Ron]

Thanks Bruno, I wish I can accept both answers at the same time, with only one click

[James Tursa]

I gave Bruno a vote since he contributed a key part of the solution.

Answer 2

[Bruno Luong]

prefered_order = 'xzy';

b = [x y z]; % logical conditions (in if/elseif)
code_to_be_exec = { @xcode, @ycode, @zcode }; % code in the if elseif block put in functions
[~,i] = ismember(prefered_order, 'xyz');
j = find(b(i), 1, 'first');
if ~isempty(j)
    feval(code_to_be_exec{i(j)});
end

[Rub Ron]

do you think there is a way to preseve the if elseif structure? for easy-to-read purpose.

[Bruno Luong]

Of course, unroll all 6 possible permutations

if strcmp(prefered_order, 'xyz')
    % your original if/else
elseif strcmp(prefered_order, 'yxz')
  % another order...

elseif strcmp(prefered_order, 'zyx')
   ....
end

Answer 3

[KSSV]

Are you looking something like this.

if z  
    %code for case z    
    order = ['case','z'] ;
elseif x
    %code for case x
    order = ['case','x'] ;
elseif y 
    %code for case y  
    order = ['case','y'] ;
end

[Rub Ron]

Hi, no. What I want is to chance the order of the if else if statement, base on a variable order that indicates which order should be considered. Is it clear what I am trying to achieved?

[KSSV]

order = 'z'
if strcmpi(order,'z')
    %code for case z    
    order = ['case','z'] ;
elseif strcmpi(order,'x')
    %code for case x
    order = ['case','x'] ;
elseif strcmpi(order,'y')
    %code for case y  
    order = ['case','y'] ;
end

Also have a look on switch.

[Rub Ron]

I updated my post, hopefully now it is clearer.