the purpose of %f

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Umut Oskay 2020-4-5

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评论： Umut Oskay 2020-4-5

采纳的回答： John D'Errico

i know what %d is but i want to know what is %f and is there any difference between %d and %f?

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Answer 1

John D'Errico 2020-4-5

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编辑：John D'Errico 2020-4-5

在 MATLAB Online 中打开

They seem identical to me. See? The result is exactly the same. ;-)

sprintf('%d',pi)
ans =
    '3.141593e+00'
    
sprintf('%f',pi)
ans =
    '3.141593'    

Or here:

sprintf('%d',137)
ans =
    '137'
sprintf('%f',137)
ans =
    '137.000000'

%d would typically be used to display signed integers, as in the second example, or in this next one.

sprintf('%10d',-137)
ans =
    '      -137'
sprintf('%10f',-137)
ans =
    '-137.000000'

%f applies to floating point numbers.

The caveat is, if the number is actually a floating point number, but you used %d, then MATLAB must do something. Reading the help docs for sprintf, I found this comment:

If you specify a conversion that does not fit the data, such as a text conversion for a numeric value, MATLAB® overrides the specified conversion, using instead %e.

Now, go back to the first example I showed. Consider which format was used there.

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Umut Oskay 2020-4-5

thanks alo t

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Answer 2

Walter Roberson 2020-4-5

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On output, %d is intended for signed integer; %f is intended for fixed-point representation.

On input formats, such as textscan(), %d by itself is intended to read a signed integer that fits into 32 bits and is output as int32 data type, whereas %f is intended to read floating point numbers and return double precision. There are variations such as %d16 for 16 bit signed integers.

https://www.mathworks.com/help/matlab/ref/textscan.html#btghhyz-1-formatSpec

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Walter Roberson 2020-4-5

For example, if you create an 8 bit integer, then you can either use it to store the numbers 0 to 255 (unsigned --> all non-negative) or -128 to 127 (signed, potentially negative)

Umut Oskay 2020-4-5