When it comes to naming variables, some people prefer camel casing (e.g. GearRatio); some prefer underscore (e.g. gear_ratio); and others prefer lowercase abbreviations (e.g. gr). We may also develop our own naming convention. But whichever we use, we should keep to one style throughout.
To change a variable's name, use rename oldvar newvar.
. rename rep78 repair_record
Each variable can have a label attached to it, which provides more information of a variable.
label variable varname “label” attaches a label to a variable.
. label variable rep78 “repair_record_78”
When browsing the auto data, you may have noticed that the foreign variable has values of characters in blue. This means that it is a numeric variable with labeled values. If you see the values in red, then it is a string variable. The black values are numbers.
We will discuss how to define variable value labels below.
label define and label values attach value labels to a numeric variable in two steps:
label define labelname # label # label … first creates a label name for all the labels we are going to attach to the variable values .
label values var labelname then matches the labels to the values.
For instance,
. sysuse auto
. gen priceIndicator = (price >= 5000 & price < .)
. label define priceLabel 0 affordable 1 expensive
. label values priceIndicator priceLabel
first creates an indicator variable based on an arbitrary standard of affordability (price<5000), and then attaches the labels of “affordable” to the numeric value 0 and “expensive” to 1.
. codebook priceIndicator
------------------------------------------------------------------------------------------
priceIndicator (unlabeled)
------------------------------------------------------------------------------------------
type: numeric (float)
label: priceLabel
range: [0,1] units: 1
unique values: 2 missing .: 0/74
tabulation: Freq. Numeric Label
37 0 affordable
37 1 expensive
Once we got the value label name, we can list the labels for each value of the variable.
label list labelname returns a list.
. label list priceLabel
priceLabel:
0 affordable
1 expensive
In fact, in the auto data, variable foreign came with attached value lables.
. codebook 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
. label list origin
origin:
0 Domestic
1 Foreign
label drop labelname removes the value labels from a variable.
. label drop priceLabel