Introduction to Stata 8 - (GRIPS

generate; replace [R] generate
Generate a new variable by:
generate bmi=weight/(height^2)
If the target variable (bmi) already exists in the data set, use replace:
replace bmi=weight/(height^2)
Do a conditional calculation (males only):
generate mbmi=1.1*bmi if sex==1
Besides the standard operators there are a number of functions: [U] 16.3
generate y=abs(x) absolute value |x|
gen y=exp(x) exponential, e x
gen y=ln(x) natural logarithm
gen y=log10(x) base 10 logarithm
gen y=sqrt(x) square root
gen y=int(x) integer part of x. int(5.8) = 5
gen y=round(x) nearest integer. round(5.8) = 6
gen y=round(x, 0.25) round(5.8, 0.25) = 5.75
gen y=mod(x1,x2) modulus; the remainder after dividing x1 by x2
gen y=max(x1,...xn) maximum value of arguments
gen y=min(x1,...xn) minimum value of arguments
gen y=sum(x) cumulative sum across observations, from first to current obs.
gen y=_n _n is the observation number
gen y=_N _N is the number of observations in the data set
egen [R] egen
egen (extensions to generate) gives some more useful functions. It may be confusing that
functions working differently with generate and egen have the same names, so take
care. Here are some examples:
Generating the same value for all observations
egen meanage=mean(age) Mean age across observations
by sex: egen meange=mean(age) Mean age across observation, for each sex
egen sumage=sum(age) Sum of age across all observations (unlike
generate's sum)
egen maxage=max(age) Maximum value of age across observations
egen minage=min(age) Minimum value af age across observations
Generating individual values for each observation (each row)
egen minq=rmin(q1-q17) Min. value of q1-q17 for this observation
egen maxq=rmax(q1-q17) Max. value of q1-q17 for this observation
egen meanq=rmean(q1-q17) Mean value of q1-q17 for this observation
egen sumq=rsum(q1-q17) Sum of q1-q17 for this observation
egen valq=robs(q1-q17) Number of non-missing q1-q17 for this observation
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