Help with error command and user input

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Stevie Rauch
Stevie Rauch 2020-4-18
评论： Sriram Tadavarty 2020-4-18
Below I have a simple user input asking for an angle. I am currently displaying an error if the user does not pick a valid angle, they will then have to rerun the code in order to try again. I am trying to have a while loop that doesn't continue on until the statement is true but I am having trouble with my arguments. I originally tried,
A = input('Pick an angle 15, 30, 45 or 60 degreees. Angle = ');
while A ~= [15 30 45 60]
A = input('Pick an angle 15, 30, 45 or 60 degreees. Angle = ');
if A ~= [15 30 45 60]
error('angle must be 15, 30, 45, or 60 degrees');
end
end
but this brings a problem because the if statement is never reached. Currently i have
A = input('Pick an angle 15, 30, 45, or 60 angle = ');
if A ~= ([15 30 45 60])
error('angle must be 15, 30, 45, or 60 degrees ');
end
any help is appreciated.

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回答（1 个）

Sriram Tadavarty
Sriram Tadavarty 2020-4-18
Hi Stieve,
You can try running the infinite loop, till the input provided is one of the valid values.
Once, you place the error in the code, the execution stops. Indeed you can place the message with the disp command.
Here is the way the code can be placed.
A = input('Pick an angle 15, 30, 45 or 60 degreees. Angle = ');
while (1)
if any(A == [15 30 45 60])
break;
else
disp('angle must be 15, 30, 45, 0r 60 degrees') % This is to indicate what the valid values are
A = input('Pick an angle 15, 30, 45 or 60 degreees. Angle = ');
end
end
Hope this helps.
Regards,
Sriram
  2 个评论
Stevie Rauch
Stevie Rauch 2020-4-18
Ahh I see so one cannot prompt the user for an input after an error message in the code. They simply have to restart it?
Sriram Tadavarty
Sriram Tadavarty 2020-4-18
If you use error command, then they have to restart the code. You can use warning or disp as suggested.
error will stop the execution once it reaches it.
Hope this helps.
Regards,
Sriram

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