Tables and axes > More about axes > Redefining a base
 
Redefining a base
Tables can contain several base elements. The most common occurrence of a second or redefined base is in preference tables as in the example above. Percentages for the products themselves are calculated using the number of respondents eligible for inclusion in the table, while percentages for the reasons for preference are generated using the number of people preferring that product as a base.
You can also have the reasons for preference percentaged against the table base. This is done with the option op=6 on the a, flt or tab statement. For more information about output types, see Output options.
When the two sets of percentages are printed, the percentage against the redefined base (for example, all preferring product A) will be printed on the line immediately beneath the absolute figures, with the percentages against the table base on the line below.
The table below provides an example. The table is created by the statement:
tab pref region;op=126
pref is as follows:
l pref
col 145;Base;hd=Product Preferred;Brand A;Brand B;Brand C
n00;c=c145'1'
col 146;Base=All Preferring A;Cleans Better;Pleasant Smelling;
+Lots of Bubbles; ...
n00;c=c145'2'
col 146;Base=All Preferring B; ....
                   Detergent Survey                      Page 13
                                      Absolutes/Col Percentages
Base: All Respondents
                                         Region
                       Base    North    South    East    West
                       ----    -----    -----    ----    ----
Base                    282       78       81      57      66
Product Preferred
Brand A                 110       37       42      21      10
                       39.0%    47.4%    51.9%   36.8%   15.2%

Brand B                  95       15       28      15      37
                       33.7%    19.2%    34.6%   26.4%   56.1%

Brand C                  77       26       11      21      19
                       27.3%    33.4%    13.5%   36.8%   28.7%

All Preferring A        110       37       42      21      10

Cleans Better            50       13       20      11       6
                       45.5%    35.1%    47.6%   52.4%   60.0%
                       17.7%    16.7%    24.7%   19.3%    9.1%

Pleasant Smelling        27        9       12       5       1 
                       54.0%    24.3%    28.6%   23.8%   10.0%
                        9.6%    11.5%    14.8%    8.8%    1.5%

Lots of Bubbles          33       15       10       5       3
                       30.0%    40.6%    23.8%   23.8%   30.0%
                       11.7%    19.2%    12.4%    8.8%    4.5%

All Preferring B         95       15       28      15      37
                 .
There are several minor variations which would work just as well: for example, in place of the n00s and the Base parameters on the col statements you could use n10s with conditions on them. However, this would mean replacing the cols with separate n01s for each element and adding the condition to each of those statements as well. Alternatively, since the same col statement applies to all brands and the n00 is almost the same, you could put them in a separate file and include it in the relevant places with an *include statement. For more information about the inclusion of files in this way, see Include and substitution.
See also
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