return value of [ ] for an 'if' or 'for' function

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Elena
Elena on 23 Feb 2022
Commented: Akira Agata on 23 Feb 2022
Say I have any function and the input can be input = 123.
For this function, only numbers can work as the input or else the return value should be [ ].
So if i were to have input = 'abc', the return value would need to show [ ].
How can I do this? If the input passes that first test it needs to be able to run the rest of the code.
Here is something i tried, it did not work.
Distance = 'abc'
if Distance = lettersPattern
res = []
end
Additionally, how can i also link the part abvoe to another requisite. If the input is empty to say 'unknown'?
if isempty(cLine)
res = 'unknown'
end

Accepted Answer

Akira Agata
Akira Agata on 23 Feb 2022
How about the following?
function output = yourFunction(input)
if isempty(input)
output = 'unknown';
elseif isa(input,'numeric')
output = input;
else
output = [];
end
end
  1 Comment
Akira Agata
Akira Agata on 23 Feb 2022
Well, in that case the Regular expression will work, like:
function output = yourFunction2(input)
str = regexp(input,'^\d{3}-\d{2}-\d{2}$','match');
if ~isempty(str)
output = input;
else
output = [];
end
end
For example:
>> yourFunction2('000-01-00')
ans =
'000-01-00'
>> yourFunction2('000-01-0a')
ans =
[]

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