Why does str2num truncate my number so early?

Question

Andrew Reibold 2014-6-23

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https://ww2.mathworks.cn/matlabcentral/answers/137171-why-does-str2num-truncate-my-number-so-early

评论： Jairo Andrés Gutiérrez Suárez 2022-2-7

When I try to convert from string to number, I lose precision?

   whos test_str
    Name          Size            Bytes  Class    Attributes
    test_str      1x9                18  char               
K>> test_str
test_str =
0.067354
K>> str2num(test_str)
ans =
      0.0674

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Answer 1

José-Luis 2014-6-23

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https://ww2.mathworks.cn/matlabcentral/answers/137171-why-does-str2num-truncate-my-number-so-early#answer_142097

在 MATLAB Online 中打开

 format long
 str2num(test_str)

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Andrew Reibold 2014-6-23

Thank you Jose-Luis

This worked great. I presume that this changes the format for any future things I type as well?

Does anyone know what is the 'default' format if it is not long?

José-Luis 2014-6-23

在 MATLAB Online 中打开

You could read the documentation:

doc format

Note that this only changes how the number is displayed. Its internal representation is, by default in Matlab, a double.

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Answer 2

Sara 2014-6-23

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https://ww2.mathworks.cn/matlabcentral/answers/137171-why-does-str2num-truncate-my-number-so-early#answer_142092

在 MATLAB Online 中打开

Use

sprintf

so you can control the precision you want.

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Sara 2014-6-23

I read it the other way around, sorry.

Jairo Andrés Gutiérrez Suárez 2022-2-7

Yep but that method is not efficient. There should be a way to use the exact number of decimals. What if I am using srt2num to find a folder with the same number I looked for?

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