Introduction to Stata 8

ecode [R] recode
Changes a variable's values, e.g. for grouping a continuous variable into few groups. The
inverted sequence ensures that age 55.00 (at the birthday) goes to category 4:
recode age (55/max=4)(35/55=3)(15/35=2)(min/15=1) , generate(agegr)
Value labels for the new variable may be included at once:
recode age (55/max=4 "55+")(35/55=3 "35-54")(15/35=2 "15-34") ///
(min/15=1 "-14") , generate(agegr)
Very important: The generate option creates a new variable with the recoded
information; without generate the original information in age will be destroyed.
Other examples:
recode expos (2=0) Leave other values unchanged
recode expos (2=0) , gen(exp2) Values not recoded transferred unchanged
recode expos (2=0) if sex==1 Values not recoded (sex != 1) set to missing
recode expos (2=0) if sex==1 , copy Values not recoded (sex != 1) unchanged
recode expos (2=0)(1=1)(else=.) Recode remaining values to missing (.)
recode expos (missing=9) Recode any missing (., .a, .b etc.) to 9
Another way to recode continuous data into groups: [R] egen
egen agegrp=cut(age) , at (0 5(10)85 120)
age agegrp
0 ≤ age < 5 0
5 ≤ age < 15 5
15 ≤ age < 25 15
.. ..
85 ≤ age < 120 85
for
Enables you with few command lines to repeat a command. To do the modulus 11 test for
Danish CPR numbers (see section 15.3) first multiply the digits by 4,3,2,7,6,5,4,3,2,1; next
sum these products; finally check whether the sum can be divided by 11. The CPR numbers
were split into 10 one-digit numbers c1-c10:
generate test = 0
for C in varlist c1-c10 \ X in numlist 4/2 7/1 : ///
replace test = test + C*X
replace test = mod(test,11) // Remainder after division by 11
list id cpr test if test !=0
C and X are stand-in variables (names to be chosen by yourself; note the use of capital
letters to distinguish from existing variables), to be sequentially substituted by the elements in
the corresponding list. Each list must be declared by type; there are four types: newlist
(list of new variables), varlist list of existing variables, numlist (list of numbers),
anylist (list of words).
for is not documented in the manuals any more. The foreach and forvalues
commands partially replace it, but they don't handle parallel lists as shown above. See section
15.7.
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