How can I to convert a cell to a double without losing the leading zeros?

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pink flower 2020-9-20

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https://ww2.mathworks.cn/matlabcentral/answers/596698-how-can-i-to-convert-a-cell-to-a-double-without-losing-the-leading-zeros

评论： Star Strider 2020-9-20

I have a loop where I am trying to extract the numbers and convert them to double. However, when the numbers are "0000", the result is just "0". How can I do this?

for x = 1:length(ix20); 
        
        namex = files(i).name;
        sss=regexp(namex, '(?:\d{4})\>','match');
        format longg;
        hm(x)=str2double(sss);
        
    end

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David Hill 2020-9-20

I don't understand what you are trying to do. Please explain with an example (input and expected output). The double of '0000' is 0.

pink flower 2020-9-20

This is an hour and minute data. I need to put them in an array, so I'm trying to do this cell to double transformation.

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Answer 1

Star Strider 2020-9-20

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/596698-how-can-i-to-convert-a-cell-to-a-double-without-losing-the-leading-zeros#answer_497401

Thank you for quoting my code from Extracting numbers from mixed string !

It is not possible to retain leading zeros in a numeric representation, such as double. To retain leading zeros, they must be kept as character arrays (single quotes) or string variables (double quotes).

I would appreciate it if you would Accept my Answer that uses the regexp call you quoted!

.

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pink flower 2020-9-20

This is an hour and minute data. I need to put them in an array, so I'm trying to do this cell to double transformation. Can I do this without losing 0000?

Star Strider 2020-9-20

在 MATLAB Online 中打开

The leading zeros would disappear if your converted them to numeric values.

If you want to convert them to datetime arrays, that would be straightforward:

out = compose("%04d", 0:5:20).'
DT = datetime(out, 'InputFormat',"HHmm", 'Format','HH:mm')

producing:

out = 
  5×1 string array
    "0000"
    "0005"
    "0010"
    "0015"
    "0020"
DT = 
  5×1 datetime array
   00:00
   00:05
   00:10
   00:15
   00:20

The ‘DT’ vector would then be saved as a datetime array (call it anything you wish), with the leading zeros intact, and converted to hours and minutes as well. (The 'InputFormat' string specifies how the input is parsed, and the 'Format' string specifies how it is displayed.)

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