Help with IF/Else statement in GUI
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Hi guys, i am new here. :) I have a problem with IF/Else statement, but only in GUI. If i put only one if statement, like this
if s=='Add'
f=x+y;
end
It works, but when i add this:
if s=='Add'
f=x+y;
end
if s=='Substract'
f=x-y;
end
It doesn't work.Also, if i only use
if s=='Substract'
f=x-y;
end
it works.I don't have a clue why is this happening.Any idea?
采纳的回答
There is not connection to the fact, that the code "runs in a GUI" - by the way: there is even nothing like "running in GUI". Code is code.
The problem is the comparison of a string the the == operator, which performs an elementwise comparison. If the compared strings have a different number of characters, such a comparison must fail.
Use strcmp instead:
if strcmp(s, 'Add')
f = x+y;
end
if strcmp(s, 'Substract')
f = x-y;
end
Or with switch/case:
switch s
case 'Add'
f = x+y;
case 'Subtract'
f = x-y;
otherwise % No SWITCH without OTHERWISE!
error('Unexpected value of [s]');
end
Note: In your question you write "doesn't work". Please post the complete error message in the future, because these messages contain valuable information to solve the problem.
更多回答（2 个）
jack int
2017-5-16
0 个投票
1 个评论
Jan
2017-5-16
Then please read my answer, where I explained the problem with using the == operator:
'test' == '1234'
This replies [false, false, false, false]. In the IF command you want a scalar condition. Therefore Matlab converts the expression internally to:
if all(s=='Add') && ~isempty(s=='Add')
Now try:
'test' == '123'
You get an error message, because an elementwise comparison is not working.
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