encode var, gen(newvar) creates a numeric variable newvar by assigning a numeric value to each of var's string value. It provides a mapping between the numeric value and the value label.
. sysuse auto
. encode make, gen(make_num) creates the numeric variable make_num.
. label list make_num gives us the mapping between the numeric values and the labels of the newly defined numeric variable make_num.
make_num:
1 AMC Concord
2 AMC Pacer
3 AMC Spirit
4 Audi 5000
5 Audi Fox
6 BMW 320i
7 Buick Century
8 Buick Electra
9 Buick LeSabre
10 Buick Opel
11 Buick Regal
12 Buick Riviera
13 Buick Skylark
14 Cad. Deville
15 Cad. Eldorado
16 Cad. Seville
17 Chev. Chevette
18 Chev. Impala
19 Chev. Malibu
20 Chev. Monte Carlo
21 Chev. Monza
22 Chev. Nova
23 Datsun 200
24 Datsun 210
25 Datsun 510
26 Datsun 810
27 Dodge Colt
28 Dodge Diplomat
29 Dodge Magnum
30 Dodge St. Regis
31 Fiat Strada
32 Ford Fiesta
33 Ford Mustang
34 Honda Accord
35 Honda Civic
36 Linc. Continental
37 Linc. Mark V
38 Linc. Versailles
39 Mazda GLC
40 Merc. Bobcat
41 Merc. Cougar
42 Merc. Marquis
43 Merc. Monarch
44 Merc. XR-7
45 Merc. Zephyr
46 Olds 98
47 Olds Cutl Supr
48 Olds Cutlass
49 Olds Delta 88
50 Olds Omega
51 Olds Starfire
52 Olds Toronado
53 Peugeot 604
54 Plym. Arrow
55 Plym. Champ
56 Plym. Horizon
57 Plym. Sapporo
58 Plym. Volare
59 Pont. Catalina
60 Pont. Firebird
61 Pont. Grand Prix
62 Pont. Le Mans
63 Pont. Phoenix
64 Pont. Sunbird
65 Renault Le Car
66 Subaru
67 Toyota Celica
68 Toyota Corolla
69 Toyota Corona
70 VW Dasher
71 VW Diesel
72 VW Rabbit
73 VW Scirocco
74 Volvo 260
decode var, gen(newvar) works the other way around. It creates a string variable newvar using the value labels attached earlier to the numeric variable var.
. decode foreign, gen(foreign_str) creates a string variable that has two values “Domestic” and “Foreign”.
. codebook foreign_str
-----------------------------------------------------------------------------------
foreign_str Car type
-----------------------------------------------------------------------------------
type: string (str8)
unique values: 2 missing "": 0/74
tabulation: Freq. Value
52 "Domestic"
22 "Foreign"
-----------------------------------------------------------------------------------
foreign Car type
-----------------------------------------------------------------------------------
type: numeric (byte)
label: origin
range: [0,1] units: 1
unique values: 2 missing .: 0/74
tabulation: Freq. Numeric Label
52 0 Domestic
22 1 Foreign
destring/tostring, replace or destring/tostring, generate() converts string variables to numeric variables and vice versa.
. tostring make_num, gen(make_str) converts the numeric variable make_num previously encoded from make back to a string variable but with values in numbers rather than alphabetical letters.
. codebook make_str
-----------------------------------------------------------------------------------
make_str Make and Model
-----------------------------------------------------------------------------------
type: string (str2)
unique values: 74 missing "": 0/74
examples: "21"
"35"
"49"
"62"
. destring make_str, replace converts make_str to a numeric variable.
. codebook make_str
-----------------------------------------------------------------------------------
make_str Make and Model
-----------------------------------------------------------------------------------
type: numeric (byte)
range: [1,74] units: 1
unique values: 74 missing .: 0/74
mean: 37.5
std. dev: 21.5058
percentiles: 10% 25% 50% 75% 90%
8 19 37.5 56 67
string(n) and real(s) are two string functions that convert numeric/string to string/numeric variables.
string(n) is a synonym for strofreal(n) and converts numeric or missing values to strings.
. sysuse auto
. gen rep78_str = string(rep78) converts the numeric and missing values of rep78 to strings.
real(s) converts strings to numeric or missing values. The string variable must contain number characters, otherwise missing values will be generated.
. gen rep78_str_num = real(rep78_str) converts the string variable rep78_str created above back to numeric again.
label define creates labels to each value of a numeric variable.
encode works on strings. It creates a new variable, and assigns a numeric value to each of the string value.
decode works on numeric variables that has attached value labels. It creates a new string variable that gets its variable values from the previous label values.
destring works on string variables that contain numbers stored as strings, and converts them to numbers.
tostring converts numeric variables to strings.
real()/string() functions convert strings/numeric variables between each other, but cannot be used just by themselves.