if statment. why do i receive following statment: Operands to the || and && operators must be convertible to logical scalar values.

Hi all plz help me.I don't understand why following code is not working..

choice=input('enter something:','s');

if str2num(choice)==1 lower(choice) == 'load the data'

    disp('loading the data')

end

when i run the code matlab says following:

Operands to the and && operators must be convertible to logical scalar values.

thx..

Answer 1

[Geoff Hayes]

The error is occurring when the user enters a choice that is non-numeric and the conversion from str2num is empty (i.e. []) which is NOT a logical scalar value operand to the (missing?) or () operator. (In the Command Window type str2num('hello') and observe the result.)

To get around this, you could convert the string to a number and check that it is not empty and equal to one, OR compare the string

 choiceStr = input('enter something:','s');
 choiceNum = str2num(choiceStr);

 if (~isempty(choiceNum) && choiceNum==1) || lower(choiceStr) == 'load the data'
     disp('loading the data');
 end

Even the above is not quite correct. When comparing strings it is preferable to use the strcmp or strcmpi functions. Since you are not interested case (because of the lower) then just use strcmpi

 choiceStr = input('enter something:','s');
 choiceNum = str2num(choiceStr);

 if (~isempty(choiceNum) && choiceNum==1) || strcmpi(choiceStr,'load the data')==1
     disp('loading the data');
 end

Try the above and see what happens!