set order of elseif

Question

Rub Ron 2020-12-17

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/696325-set-order-of-elseif

评论： James Tursa 2020-12-17

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.

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Ive J 2020-12-17

编辑：Ive J 2020-12-17

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 2020-12-17

Have a look on switch.

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Answer 1

James Tursa 2020-12-17

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https://ww2.mathworks.cn/matlabcentral/answers/696325-set-order-of-elseif#answer_578470

编辑：James Tursa 2020-12-17

在 MATLAB Online 中打开

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.

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Rub Ron 2020-12-17

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

James Tursa 2020-12-17

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

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Answer 2

Bruno Luong 2020-12-17

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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

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Rub Ron 2020-12-17

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

Bruno Luong 2020-12-17

编辑：Bruno Luong 2020-12-17

在 MATLAB Online 中打开

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

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Answer 3

KSSV 2020-12-17

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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

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KSSV 2020-12-17

在 MATLAB Online 中打开

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