MATLAB: Print numbers in Enginering Notation

engineering notation

Hi everyone,

I need to print out in a txt file a list of numbers, one for each row, with this format:

i.dddddddddddddde+000 hence 1digit before decimal separator, 14 after that and 3 for the exponent.

Could anyone help me?

Thanks,

Stefano

Best Answer

Separate the mantissa and the exponent

   Values = [pi ; 1.12301230123e17 ; 100000 ; 9999999999999]
   E = floor(log10(Values))  % exponent
   M = Values ./ (10.^E)     % mantissa
   TMP = [M(:) E(:)].'
   fprintf('%1.14fe%03d\n', TMP)

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Not only Matlab's double type uses about 16 digits, but this is the IEEE754 standard, which is available in all numerical software and usual processors. Besides Walter's suggestion to use '%.16g', which is more suitable e.g. for pi*1e14, the conversion to the decimal number as an ASCII file must reduce the precision. Example:

a = pi * 1e16;
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The conversion from the binary double format to the decimal text format includes a certain loss of precision already. When you want to deliver the values accurately, store them in binary format:

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You can read the binary format from the C++ function also. And the import is faster than the conversion from the string.

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You forget a fprintf(fid2,... line, so you are not writing anything with this code, just open and close the phone.txt file.

you need to complete this

fid=fopen('phonenos.csv','r');
fid2=fopen('phone.txt','w');
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    phonenos=fgetl(fid);
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    next3=phonenos(4:6);
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