logarithmic rounding

roundl is a MATLAB function that does base-10 logarithmic rounding.

Syntax:

y= roundl(x, mode, n)

The value y is x rounded to a number of the form a*10^n, where n is an integer and a is one of a small number of multipliers.

x, the number to be logarithmically rounded, must be positive.

mode (optional) specifies the rounding direction. If specified, mode must be 'u' (round up), 'd' (round down), or 'n' (round to nearest); 'n' is the default.

n (optional) specifies the number of values per decade and thus determines the allowed multipliers. Allowed values of n are 1-7. The default value for n is 3; n= 5 and n= 7 are not commonly used. The following table shows the set of multipliers for each value of n:

1: 1
2: 1, 3
3: 1, 2, 5
4: 1, 2, 3, 5
5: 1, 2, 3, 5, 7
6: 1, 1.5, 2, 3, 5, 7
7: 1, 1.5, 2, 3, 4, 6, 8