Introduction to Stata 8

. tab1 rating type (table for type not shown)
-> tabulation of rating
quality |
rating | Freq. Percent Cum.
--------------+-----------------------------------
1. poor | 6 17.14 17.14
2. acceptable | 9 25.71 42.86
3. good | 16 45.71 88.57
4. excellent | 4 11.43 100.00
--------------+-----------------------------------
Total | 35 100.00
tab2 [R] tabulate
tab2 with two variables give a two-way table (crosstable). In the following you see the use
of three options. column requests percentage distributions by column; chi2 a χ 2 test, and
exact a Fisher's exact test:
. tab2 rating type , column chi2 exact
->
tabulation of rating by type
quality | type of wine
rating | 1 red 2 white 3 rosé 4 undeter | Total
--------------+--------------------------------------------+----------
1. poor | 4 1 1 0 | 6
| 25.00 9.09 20.00 0.00 | 17.14
--------------+--------------------------------------------+----------
(Part of output omitted)
--------------+--------------------------------------------+----------
4. excellent | 2 1 0 1 | 4
| 12.50 9.09 0.00 33.33 | 11.43
--------------+--------------------------------------------+----------
Total | 16 11 5 3 | 35
| 100.00 100.00 100.00 100.00 | 100.00
Pearson chi2(9) = 6.9131 Pr = 0.646
Fisher's exact = 0.653
You can request a three-way table (a two-way table for each value of nation) with:
bysort nation: tabulate rating type
The command:
tab2 rating type nation
gives three two-way tables, one for each of the combinations of the variables. But beware:
you can easily produce a huge number of tables.
[P] foreach
Imagine that you want 10 two-way tables: each of the variables q1-q10 by sex. With
tabulate you must issue 10 commands to obtain the result desired. If you call tab2 with
11 variables you get 55 two-way tables: all possible combinations of the 11 variables. The
foreach command (see section 15.7) lets you circumvent the problem:
foreach Q of varlist q1-q10 {
tabulate `Q' sex
}
The local macro Q is a stand-in for q1 to q10, and the commands generate 10 commands:
tabulate q1 sex
tabulate q2 sex etc.
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