Find only numeric strings on cellstr array.

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Ajpaezm
Ajpaezm 2021-6-15
评论： Ajpaezm 2021-6-15
I'd like to know the index of the "numerical strings" within a cellstr array.
arr = {'123', 'Hola', 'my', 'String', '', '1453', 'stay'};
A correct output will give me index 1 and 6.
isnumeric contained within cellfun doesn't work well here, I'd have to use it in combination with something else but I don't know exactly what that might be.
Any help is appreciated.

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采纳的回答

Krishna Sutar
Krishna Sutar 2021-6-15
From my understanding you want to find the indexes of the strings in the cell string array that are numerical. Here is the code which might help you:
arr = {'123', 'Hola', 'my', 'String', '', '1453', 'stay'};
idx = find(~isnan(str2double(arr)))
isnumeric checks whether the datatype of the object is numeric, which in this case is string which would return false. Please refer to isnumeric and find for more information.
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Stephen23
Stephen23 2021-6-15
Note that this code will incorrectly mark 'NaN' as not numeric.
Ajpaezm
Ajpaezm 2021-6-15
@Stephen Cobeldickthank you, I understand. Luckily, the array won't have any presence of them, but in case some weird stuff happens and indeed gets populated with it, I'll be sure to use your proposal.

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更多回答（2 个）

Walter Roberson
Walter Roberson 2021-6-15
Ran in:
arr = {'123', 'Hola', 'my', 'String', '', '1453', 'stay'};
find(~cellfun(@isempty, regexp(arr, '^\d+$', 'once')))
ans = 1×2
1 6
find(matches(arr, lineBoundary + digitsPattern + lineBoundary))
ans = 1×2
1 6
Stephen23
Stephen23 2021-6-15
编辑：Stephen23 2021-6-15
Ran in:
Writing regular expressions or pattern matching that robustly detects all valid number formats is not such a trivial task... it is more reliable to let MATLAB do the heavy lifting:
arr = {'123', 'Hola', 'my', 'String', '', '1453', 'stay', '-1.234', 'NaN', '9e-87'};
idx = strcmpi(arr,'NaN')|~isnan(str2double(arr))
idx = 1×10 logical array
1 0 0 0 0 1 0 1 1 1
find(idx)
ans = 1×5
1 6 8 9 10

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