How to check if an entire column of string variables can potentially be converted to numerical values?

Question

Leon 2019-10-17

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https://ww2.mathworks.cn/matlabcentral/answers/485995-how-to-check-if-an-entire-column-of-string-variables-can-potentially-be-converted-to-numerical-value

回答： Matt J 2019-10-18

I have a column variable normally look like this:

'ABC1234'
'DEC1236'
'CFG5645'
... 

Once in a while the column data will be like this, i.e., composed entiredly of strings that can be converted to numerical values.

'1234567'
'2312456'
'7863522'
...

When this happens, I want to use str2num to convert them into numerical values first before using writetable to put them into an Excel file. Otherwise, I would see all those yellow diamonds with ! inside next to each row of the column to indicate errors.

So how do I detect if all elements in an entire column can potentially be converted to numerical values?

Also when I treid to use str2num, why am I getting the below error?

Input must be a character vector or string scalar.

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Leon 2019-10-17

Cool. It works! I did not know there is a str2double() before.

Thank you so much.

Guillaume 2019-10-17

编辑：Guillaume 2019-10-17

As the documentation of str2num states, it's a dangerous function to use (internally it uses eval so I could give you a string that would delete everything on your hard drive were you to pass it to str2num.)

Whenever possible prefer str2double which is guaranteed to not have any side effect.

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