Switch expression must be a scalar or string constant -- Matlab GUI

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Giuseppe Napoli
Giuseppe Napoli 2017-7-20
评论： Jan 2017-7-20
Hello to everyone,
I am creating a GUI where a user can select with radio button three different type of steels. For the first two type, I don't have a problem because I call "304" and "316". The third option instead is a string value called "STR18" and when I try to execute my script Matlab says " Switch expression must be a scalar or string constant". I think that the problem could be in the variable "steeltype", but I am not sure. How can I solve my problem? How can I use, at the same time, numbers and string for the switch function ?
Thanks in advance
function pushbutton1_Callback(hObject, eventdata, handles)
st= get(handles.bottoni,'SelectedObject');
steeltype=str2num(get(st,'String'));
riduzione= str2num(get(handles.riduzione,'String'));
e=riduzione;
switch steeltype
case 1
......
case 2
......
case 3
......
otherwise
end
  1 个评论
Stephen23
Stephen23 2017-7-20
Why convert your perfectly nice strings into numbers? Get rid of the str2num and use strings to specify the switch cases.

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回答（1 个）

Adam
Adam 2017-7-20
编辑：Adam 2017-7-20
Just keep them all as strings. You can't convert STR18 to a number so don't convert the others either, just switch on the strings instead.
Incidentally you should use str2double rather than str2num.
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Giuseppe Napoli
Giuseppe Napoli 2017-7-20
Ok, I solved all my problem. Since I removed the str2num all the case have to put between the two apostrophe ('STR18').
Thanks all for your help. Have a nice evening.
Jan
Jan 2017-7-20
@Giuseppe: If the answer has helped you to solve the problem, please accept it.

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