Significant Figures

Version 1.8.0.0 (1.87 KB) by Teck Por Lim
Workaround for fprintf/sprintf to produce correct output for signficant figures, as fprintf/sprintf
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1.8K Downloads
Updated 9 Mar 2009

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[strOut] = sigfig(num, nSigFig, dummy)
Rounds number to nSigFig number of significant figures and outputs a string Dummy in 3rd argument to have padded zeros
Lim Teck Por, 2006, 2008,2009

Apropos: mat2str, num2str, sprintf
This code serves as a workaround to rounding problems probably caused by converting from base 10 to base 2 prematurely (Note that this problem can also be found in C and python) and print zero padding:

num2str(3.15, 2)
mat2str(3.15, 2)
fprintf('%1.2g\n', 3.15)
sprintf('%1.2g\n', 3.15)
give 3.1 instead of 3.2 whereas an input of 3.75 gives 3.8.

sigfig(3.15, 2) gives "3.2"
sigfig(3.75, 2, []) gives "3.8e+0"

Cite As

Teck Por Lim (2026). Significant Figures (https://www.mathworks.com/matlabcentral/fileexchange/10669-significant-figures), MATLAB Central File Exchange. Retrieved .

MATLAB Release Compatibility
Created with R14
Compatible with any release
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Version Published Release Notes
1.8.0.0

Support for Inf and -Inf
1.6.0.0

Allowed default nargin < 2 to mean number of significant figures = 3
Updated example.m
1.5.0.0

Updated description.
1.4.0.0

Fixed bug with sigfig(99.9999,2).
Removed leading zeros from exponent.
1.3.0.0

Bug fixed.
1.0.0.0

To enable sigfig(nan)