How does OR work in an IF statement?

Question

Geriffa 2018-5-11

0
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https://ww2.mathworks.cn/matlabcentral/answers/400255-how-does-or-work-in-an-if-statement

编辑： KSSV 2018-5-11

I want the IF statement to check the value of 'Highest_value_month' and give 'Days' a value based on that, yet 'Days' always gets the value 31. As far as I know the syntax for OR is '||'. So why doesn't my IF statement work?

Highest_value_month = 6;
 if Highest_value_month == 1 || 3 || 5 || 7 || 8 || 10 || 12
Days = 31;
elseif Highest_value_month == 2
Days = 28;
else
Days = 30;
end

The code is simplified in this case but it is essentially the same.

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Answer 1

Rik 2018-5-11

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在 MATLAB Online 中打开

Because each is treated as separate test. Therefor you will need to use something like the line below. You could also use switch and case (see second example).

if Highest_value_month == 1 || ...
        Highest_value_month == 3 || ...
        Highest_value_month == 5 || ...
        Highest_value_month == 7 || ...
        Highest_value_month == 8 || ...
        Highest_value_month == 10 || ...
        Highest_value_month == 12
    Days = 31;
end

or with switch:

switch Highest_value_month 
    case {1,3,5,7,8,10,12}
        Days = 31;
    case 2
        Days = 28;
    otherwise
        Days = 30;
end

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Answer 2

KSSV 2018-5-11

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https://ww2.mathworks.cn/matlabcentral/answers/400255-how-does-or-work-in-an-if-statement#answer_319744

编辑：KSSV 2018-5-11

在 MATLAB Online 中打开

Highest_value_month = 6;
val = [1 3 5 7 8 10 12] ;
if intersect(Highest_value_month,val)
    Days = 31;
elseif Highest_value_month == 2
    Days = 28;
else
    Days = 30;
end

OR

Highest_value_month = 12;
val = [1 3 5 7 8 10 12] ;
if ismember(Highest_value_month,val)
    Days = 31;
elseif Highest_value_month == 2
    Days = 28;
else
    Days = 30;
end