How do I round off exponential numbers?
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Nitin Samuel
on 17 Jan 2013
Commented: Walter Roberson
on 16 Nov 2015
I have a code for which I get a long exponential number eg. a = 2.572920056e-3 as the output. I need to round off only the non-exponential part i.e I want the output to be something like 2.573e-3.
I know how to round off integers using ceil, round etc, but how can one round off only the number outside the exponential like mentioned above. Also, the output varies so I cannot use a command with a fixed number like
(ceil(a*10^6)/10^6).
(The fixed number being '6' in this case).
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Accepted Answer
Walter Roberson
on 17 Jan 2013
Edited: Walter Roberson
on 17 Jan 2013
ex = 10^(3-floor(log10(a)));
ar = round(a * ex) / ex;
Caution: might not work for 0 or infinities
6 Comments
Mikhail Lisakov
on 16 Nov 2015
Edited: Walter Roberson
on 16 Nov 2015
Solution is great but fails for powers > 0 (though I've used it to round significand to integer).
To account for possible powers greater than 0 there should be a condition like this :
if(ex < 0)
ar = round(a * ex) / ex;
} else {
ar = round(a / ex) * ex;
}
Walter Roberson
on 16 Nov 2015
Different requirement, Mikhail. That formula would be for rounding decimals after the decimal point in fixed point format, but the original question was for rounding in engineering format.
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