Working with the Renard series of preferred numbers specified in ISO 3.

## Project description

The Renard series are a system of preferred numbers used in engineering applications which specifies a geometric sequence of numbers over the range one to ten. The numbers are selected to be convenient to use an to minimise the maximum relative error when an arbitrary number is replaced by the nearest Renard number. The series were proposed by the French army engineer Colonel Charles Renard and subsequently standardised in ISO 3-1973.

For example, the R5 series contains six values (1.0, 1.6, 2.5, 4.0, 6.3) which cover a one-order of magnitude range of values (one decade) from one to ten. These base values repeat again to cover the next decade from 10 to 100, as 10, 16, 25, 40, and 63.

This `renard` library is useful for selecting values from the
least rounded R5, R10, R20, R40 and R80 decades, the medium
rounded RR10, RR20 and RR40 decades, and the most rounded RRR5,
RRR10 and RRR20 decades.

## Installation

The `renard` package is available on the Python Package Index (PyPI):

The package supports Python 3 only. To install:

$ pip install renard

## Python Interface

For full help:

>>> import renard >>> help(renard)

In the meantime, here are some highlights.

To find the nearest E24 value to 319 use:

>>> from renard import find_nearest, R20 >>> find_nearest(R20, 319) >>> 315.0

To find the next value greater-than or equal-to 184 in the E96 series use:

>>> from renard import find_greater_than_or_equal, R80 >>> find_greater_than_or_equal(R80, 182) >>> 185.0

To find a few values around the specified value, use:

>>> from renard import find_nearest_few, R20 >>> find_nearest_few(R20, 5000) >>> (4500.0, 5000.0, 5600.0)

## Command-Line Interface

There’s also a handy command-line interface. Run `eseries --help`
to see a list of commands:

$ renard --help renard Usage: renard [options] <command> [<args> ...] Options: -h --help Show this screen. -v --verbose Use verbose logging Available commands: ge gt help le lt nearby nearest range series precision See 'renard help <command>' for help on specific commands.

To find a nearby value, use:

$ renard nearest R20 37726 35.5e3

If you prefer an SI exponent symbol, supply `--symbol` or `-s`:

$ renard nearest R20 37726 -s 35.5 k

To show values around the given value, use the `nearby` command:

$ renard nearby R40 52e6 -s 50 M 53 M 56 M

To show the smallest value greater than or equal to the given value, use the `ge` command:

$ renard ge R40 52e3 -s 53 k

To show all values in an inclusive range, use the `range` command:

$ renard range R5 74e-9 34e-6 -s 100 n 160 n 250 n 400 n 630 n 1 µ 1.6 µ 2.5 µ 4 µ 6.3 µ 10 µ 16 µ 25 µ

To use the most-rounded Renard R”20 series (for syntactic reasons, R‘20 is called RR20 and R” is called RRR20 on the command line):

$ renard range RRR20 10000 20000 10e3 11e3 12e3 14e3 16e3 18e3 20e3

To determine the multiple to which the base values of a series have
been rounded, use the `precision` command:

$ renard precision R5 0.01

## Project details

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