Unit conversions

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The code related to this tool is now a part of Opasnet (R library).

Question

How to convert data from one unit to another in R?

Answer

We need conversion factors, which are listed below, and a code that does the actual conversion. Function convert.units is used to perform conversions. It has three parameters:

• x: a numeric vector of values that are to be converted.
• tounit: a character vector of units that are preferred in the output. This can contain more units than needed, as long as the the entries are exclusive (i.e., only one unit for length, only one for energy etc.).
• fromunit: a character vector of units used in the input. It has (or is coerced to) the same size as x.

Composite units can be used, e.g. ug /m3. Then, each part of the unit is converted separately, e.g. micrograms to picograms and cubic metre to litres.

> convert.units(1, tounit = c("pg", "l"), fromunit = "ug /m3")

will result in

Unit	Result
pg /l	1000

Note that in the units, different parts are separated with space, but the units in the denominator must have the slash before them without a space.

What is the amount?: In what units is it?: To what units do you want it?: + Show code- Hide code out <- convert.units(amount, tounit, fromunit) cat(paste(amount, fromunit, "=", out$Result, out$Unit, "\n"))

Unit conversions(-)

Obs	From	To	Type	Result	Description
1			Prefix	1
2	da		Prefix	10	deca
3	h		Prefix	100	hecto
4	k		Prefix	1000	kilo
5	M		Prefix	1e+6	mega
6	G		Prefix	1e+9	giga
7	T		Prefix	1e+12	tera
8	P		Prefix	1e+15	peta
9	E		Prefix	1e+18	exa
10	Z		Prefix	1e+21	zetta
11	Y		Prefix	1e+24	yotta
12	d		Prefix	0.1	deci
13	c		Prefix	0.01	centi
14	m		Prefix	0.001	milli
15	μ		Prefix	1e-6	micro
16	u		Prefix	1e-6	micro
17	n		Prefix	1e-9	nano
18	p		Prefix	1e-12	pico
19	f		Prefix	1e-15	femto
20	a		Prefix	1e-18	atto
21	z		Prefix	1e-21	zepto
22	y		Prefix	1e-24	yocto
23	J	J	Unit	1	Joule, the base unit for energy
24	Wh	J	Unit	3600	1 Wh = 1 Wh * 3600 s/h = 3600 Ws = 3600 MJ
25	toe	J	Unit	3.5e+10	1 toe = 1000 kgoe = 1000 kg * 35 MJ/kg = 35000 MJ (energy as tons of oil equivalent)
26	g	g	Unit	1	gram, the base unit for mass (although the definition is based on kg)
27	ton	g	Unit	1e+6	metric ton
28	tn	g	Unit	1e+6	metric ton
29	lb	g	Unit	453.59237	international avoirdupois pound
30	s	s	Unit	1	second, the base unit for time
31	min	s	Unit	60	minute
32	h	s	Unit	3600	hour
33	d	s	Unit	86400	day
34	a	s	Unit	31557600	year (assuming 365.25 days per year)
35	m	m	Unit	1	metre, the base unit of length
36	in	m	Unit	0.0254	inch (strangely, some people still use these)
37	ft	m	Unit	0.3048	foot = 12 inches
38	mi	m	Unit	1609.344	mile = 5280 feet
39	m3	m3	Unit	1	cubic metre, the basic unit of volume
40	l	m3	Unit	0.001	litre
41	m^3	m3	Unit	1
42	A	A	Unit	1	Ampere, the basic unit of electric current
43	V	V	Unit	1	Volt, the basic unit of electric potential
44	N	N	Unit	1	Newton, the basic unit of force
45	Pa	Pa	Unit	1	Pascal, the basic unit of pressure
46	psi	Pa	Unit	6894.757	pound-force per square inch
47	bar	Pa	Unit	100000	bar
48	mol	mol	Unit	1	mole, the basic unit of substance amount
49	M	mol /l	Unit	1
50	Hz	Hz	Unit	1	Hertz, the basic unit of frequency
51	Hz	/s	Unit	1
52	C	C	Unit	1	Coulomb, the basic unit of electric quantity

See also

• An R package for converting units

Related files

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