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matlabfloating-pointdigitssignificant-digits

Rounding to n significant digits

I'm trying to write code in MATLAB that will round number to certain (as I ask) significant digits.

I'm not sure how to do it. Any suggestions?

Solution

  • To round to d significant digits:

    >> d = 3; %// number of digits
>> x = 5.237234; %// example number

>> D = 10^(d-ceil(log10(x)));
>> y = round(x*D)/D
y =
    5.2400

    To round to d decimal digits:

    >> d = 3; %// number of digits
>> x = 5.237234; %// example number

>> D = 10^d;
>> y = round(x*D)/D
y =
    5.2370

    EDIT

    Actually it's easier: the round function supports these options:

    >> d = 3;
>> x = 5.237234;
>> y = round(x, d, 'significant')
y =
    5.2400

>> d = 3;
>> x = 5.237234;
>> y = round(x, d) %// or y = round(x, d, 'decimals')
y =
    5.2370