This little function rounds a number (or the elements of a vector ot matrix) towards the nearest number with N significant digits.
roundsd(0.012345,3) returns 0.0123
roundsd(12345,2) returns 12000
roundsd(12.345,4,'ceil') returns 12.35
This is a useful complement to Matlab's ROUND, ROUND10 and ROUNDN (Mapping toolbox), especially when dealing with data with a large variety of order of magnitudes.
I was about to upload this file when I found "sd_round.m" by Edward Zechmann (see aknowledgment), which has similar feature (and more). But, because my script is very different in coding (much much shorter), I decided to share it anyway.