If statement Alternative for listdlg Index?

Question

Tobias Welby 2017-3-24

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https://ww2.mathworks.cn/matlabcentral/answers/331795-if-statement-alternative-for-listdlg-index

回答： dpb 2017-3-24

Hi all,

I'm not the most efficient programmer by any stretch, and I am currently trying to run the code below with a bit more efficiency. I feel like there must be an alternative to using an 'if statement' in the code I've attached below.

Does anybody know if could use the index value given from lisdl to minus from the areas without using numerous if statements?

I'm only asking because there is quite a few other variables in need to process in this way and i feel like i'm going to end up with such a long script.

Any help would be so greatly appreciated.

Thanks!!

x = inputdlg({'Area of Window 1','Area of Window 2','Area of Window 3','Area of Window 2'},...
              'Areas of Windows');
Window1 = str2num(x{1}); 
Window2 = str2num(x{2}); 
Window3 = str2num(x{3}); 
Window4 = str2num(x{4});
[W1] = listdlg('PromptString','What wall is Window 1 on?:',...
                'SelectionMode','single',...
                'ListString',OOL);
[W2] = listdlg('PromptString','What wall is Window 1 on?:',...
                'SelectionMode','single',...
                'ListString',OOL);
NFA = RL*RH;
SFA = RL*RH;
EFA = RW*RH;
WFA = RW*RH;
if W1 == 1          
  NFA = RL*RH-Window1;
elseif W1==2
  SFA = RL*RH-Window1; 
elseif W1==3
  EFA = RW*RH-Window1;
else
  WFA = RW*RH-Window1;
end
if W2 == 1          
  NFA = RL*RH-Window2;
elseif W1==2
  SFA = RL*RH-Window2; 
elseif W2==3
  EFA = RW*RH-Window2;
else
  WFA = RW*RH-Window2;
end

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Answer 1

dpb 2017-3-24

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Sure, that's what switch blocks are for...

switch W1
  case 1
    NFA = RL*RH-Window1;
  case 2
    SFA = RL*RH-Window1; 
  case 3
    EFA = RW*RH-Window1;
  otherwise
    WFA = RW*RH-Window1;
end

It's possible (probable?) that you could also cut down the cases as well and use arrays or other ways to keep track of conditions rather than separately-named variables. A categorical variable or the like could be an option as you've got only two separate numerically-distinct cases above with just some id difference. That could be a variable instead of a different variable and likely simplify coding later on by being able to reuse code with the different flag variable value instead of having to duplicate it to use the different variables as you now have.