Introduction to Stata 8 - (GRIPS

6. Variables
A Stata data set is rectangular; here is one with five observations and four variables:
Observations
Variables
obsno age height weight
1 27 178 74
2 54 166 67
3 63 173 85
4 36 182 81
5 57 165 90
6.1. Variable names
Variable names can be 1-32 characters, but Stata often abbreviates long variable names in
output, so I recommend to use only 8 characters. The letters a-z (but not æøå), the numbers
0-9 and _ (underscore) are valid characters. Names must start with a letter (or an
underscore, but this is discouraged because many Stata-generated variables start with an
underscore). These are valid variable names:
a q17 q_17 pregnant sex
Stata is case-sensitive
Variable names may include lowercase and uppercase letters, but Stata is case-sensitive: sex
and Sex are two different variable names. Throughout this booklet I use lowercase variable
names; anything else would be confusing.
6.2. Numeric variables [U] 15.2
Most often you don't need worry about numeric types, but if you encounter memory
problems, you should know this (see section 15.1 on Memory considerations):
Type Bytes Precision (digits) Range (approx.)
Integer byte 1 2 ±100
int 2 4 ±32,000
long 4 9 ±2×10 9
Floating point float 4 7 ±10 36
double 8 16 ±10 308
compress can reduce the size of your dataset considerably by finding the most economical
way of storage.
11