Switch/Case and operators

Question

googo 2013-3-25

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评论： samaneh 2021-5-23

I running this code and and I don't understand why it is writing me that x is less than y... can you help me figure this out?

>> x = 222, y = 3;
switch x
case x==y
disp('x and y are equal');
case x>y
disp('x is greater than y');
otherwise
disp('x is less than y');
end
x =x =
     222
x is less than y

thank's.

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Nitigya Joshi 2021-3-2

ok

samaneh 2021-5-23

Dear Googo,

The resullt of Relational Operators is Boolean meaning it takes value 1 for true and 0 for false. Hence case can only be 0 or 1 in your code, which is not desired velue for your x. That's why "otherwise" and "disp('x is less than y');" will be executed for any value of your x and y.

The solution is that, you put x beside of your Relational Operators to keep the value of the x, such as bellow.

>> x = 222, y = 3;

switch x

case x*(x==y)

disp('x and y are equal');

case x*(x>y)

disp('x is greater than y');

otherwise

disp('x is less than y');

end

%%%%%% Result %%%%%

x =

222

x is greater than y

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Answer 1

Azzi Abdelmalek 2013-3-25

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编辑：Azzi Abdelmalek 2013-3-25

在 MATLAB Online 中打开

In your case you should use if/elseif

    x = 222, y = 3;
    if x==y
        disp('x and y are equal');
    elseif x>y
        disp('x is greater than y');
    else
        disp('x is less than y');
    end

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googo 2013-3-25

Thanks for the comment! But it will be a little bit long because I need to check a specific date if the year is less then 1000 or 100 or 10 and put 3/2/1 zeros before respectivlly.. for example 1/1/800 will be 1/1/0800 same for the days and the month, if the month is less than 10... any way to shorten this out? if not... I guess I can write a number of if's but maybe there is another suggestion... thank you very much...

Azzi Abdelmalek 2013-3-25

This is not clear

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Answer 2

Jan 2013-3-25

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Don't do this. Let sprintf care about leading zeros:

a = [1,2,800];
sprintf('%d/%d/%04d', a);

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Answer 3

Benhur Tekeste 2019-2-14

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Hi, there.

From my point of view, the resullt of comparison operation is Boolean meaning it takes value 1 for true and 0 for false. Hence first the relational operation besides the case is evaluated and then compared to the expression besides the switch.

 x = 222, y = 3;
switch x
case x==y % once the program runs, it will find that x is not equal to y meaning it is false and it 
                 has   value of zero. And zero is not equal to the value of x therefore it willnot 
                        execute this body.
disp('x and y are equal');% same here too but x is greater than y it is true and has value of 1 but 
                            1 is not equal to 222 therefore body in otherwise is executed
case x>y
disp('x is greater than y');
otherwise
disp('x is less than y');
end

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Walter Roberson 2019-2-14

change the switch x to switch true and then it will work.

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Answer 4

thejas av 2021-5-20

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编辑：Walter Roberson 2021-5-20

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https://www.tutorialspoint.com/matlab/switch_statement_matlab.htm

switch(m)
     case 1
         if(d>=1 && d<=19)
             message = sprintf('\noptimistic, lovers of freedom, hilarious, fair-minded, honest and intellectual. \nThey are spontaneous and fun, usually with a lot of friends');
             %data=text( message, 'FontSize',12, 'Color', [.6 .2 .6]);
              text(-1800,800,message, 'FontSize',9, 'Color', [.6 .2 .6]);
         else
            message = sprintf('\nThey are ambitious, organized, practical, goal-oriented, and they do not mind the hustle.\n“They are ready to give up a lot in order to achieve that goal,” Verk says. \nThey also love making their own rules, which means they strive to reach high career positions.');
             %data=text( message, 'FontSize',12, 'Color', [.6 .2 .6]);
              text(-1800,800,message, 'FontSize',9, 'Color', [.6 .2 .6]);
         end
   
      case 2
         if(d>=1 && d<=19)
           message = sprintf('\nThey are ambitious, organized, practical, goal-oriented, and they do not mind the hustle.\n“They are ready to give up a lot in order to achieve that goal,” Verk says. \nThey also love making their own rules, which means they strive to reach high career positions.');
             %data=text( message, 'FontSize',12, 'Color', [.6 .2 .6]);
              text(-1800,800,message, 'FontSize',9, 'Color', [.6 .2 .6]);
         else
            message = sprintf('\n Progressive, original, independent, humanitarian\nRuns from emotional expression, temperamental, uncompromising, aloof\nFun with friends, helping others, fighting for causes, intellectual conversation, a good listener\n Limitations, broken promises, being lonely, dull or boring situations, people who disagree with them.');
             %data=text( message, 'FontSize',12, 'Color', [.6 .2 .6]);
              text(-1800,800,message, 'FontSize',9, 'Color', [.6 .2 .6]);
         end
      
 end 