|Home Page||Turf Examples|
|Turf Options||Turf Results|
|Turf Files||Turf Methods|
|Turf Timings||Turf Limitations|
TURF stands for Total Unduplicated Reach and Frequency. It is most often used in market research applications.
For example, a file has the responses of 1000 cases on 40 items. Each item is a TV program which the respondent did or did not watch.
You would like to know which group of 8 programs was reached by the largest number of respondents. A respondent is "reached" by a given group of programs if they watched at least one of the programs in the group.
TURF, to find the best group, evaluates each of the 76.9 million combinations of 8 items taken from a pool of 40, and writes a file identifying the 100 best combinations. This takes about a minute on a 2.4GHz pc.
Weighting can be applied to the cases, or to the response values, or to the items. The "being reached" criterion of one response can be increased.
Adding options affects speed. The above one-minute run takes 12 minutes if case weights are used, and would take about 30 minutes if the other options are used.
Reach and frequency are different measurements in TURF.
The REACH score for a combination is the number of cases that have at least N positive responses on the variables in that combination. N is the reach threshold in use, which has a default setting of one.
The FREQ score for a combination is, for the reached cases, normally the total number of positive responses on the variables in the combination. The response.weights option causes the FREQ score to be the sum of the positive responses.
If a case indeed watched all eight programs in a group, the frequency count for that group would be increased by 8, but the reach count would only be increased by 1.
If the input were hours watched rather than just watched or not, the response.weights option would sum the response values and thereby measure the impact of the combination.
Allows up to 210 items (i.e., variables). Allows combinations of items up to size 60. Allows several combination sizes to be done in one run. Allows tens of thousands of cases.
Allows weighting of cases. Allows weighting of items. Allows weighting of responses; this allows the intensity of a response to be utilized.
Allows setting a reach threshold of more than one. Allows forcing designated items into every combination. Allows limits on how many of a set of items can be placed in the combinations to be analyzed.
Writes a result file containing the best combinations. The items within each combination are ordered by their importance. Writes a template file for use by the TURF.SCORES command. Writes (in TURF.SCORES) the reach score for each case.
Takes 3.1 seconds for 1,000 cases on 40 items, 6 at a time on a 2.4 GHz PC. This evaluates 3.838 million groups.
Runs so rapidly that billions of combinations can be done. Takes 18.5 minutes for 1,000 cases on 100 items, 6 at a time on a 2.4 GHz PC. This evaluates 1.192 billion groups. Note: using all options would take about 9 hours.
Shows the percent of combinations already processed in a progress window. Writes a detailed report when the command finishes.
TURF results ordered by REACH, from input file tin using 29,4 pct of pct max item item item item size rank reach reached reach freq .1 .2 .3 .4 4 1 212 38.545 99.531 628 VAR3 VAR4 VAR5 VAR23 186 208 210 212 4 2 212 38.545 99.531 602 VAR3 VAR4 VAR5 VAR28 186 208 210 212 4 3 211 38.364 99.061 660 VAR3 VAR4 VAR5 VAR13 186 208 210 211 4 4 211 38.364 99.061 658 VAR3 VAR4 VAR5 VAR15 186 208 210 211 4 5 211 38.364 99.061 634 VAR3 VAR4 VAR5 VAR19 186 208 210 211
---------TURF analysis for file work2 completed---------- | OPTIONS: none | | | | 100 items were used in the analysis. | | | | 1,000 cases were read and used. | | 973 cases had at least one positive response, | | making that the maximum possible reach. | | | | SIZE 6 evaluated 1,192,052,400 combinations: | | 941 was the best REACH, found in 1 combination. | | 1,956 was the FREQ value in that combination. | | 1,983 was the best FREQ in any size 6 combination. | | | | The FREQ score for a combination is the count | | of the non-zero responses for that combination, | | summed over the reached cases. | | | | REACH.RESULTS file work101 has the 100 | | combinations with the highest reach scores. | | The items are ordered by their REACH contribution. | | Cumulative reach is shown. | | | | Time: 18 minutes, 35.5 seconds. | ---------------------------------------------------------
The following links complete the online TURF documentation. They are:
This shows a small dataset and four TURF runs, done with
differing options. The output is explained. These show the
effects of item, response and case weighting, as well as
the effect of using a reach threshold of more than 1.
TURF.OPTIONS This describes all of the TURF identifiers.
TURF.RESULTS The principle output from most TURF runs is the REACH.RESULTS file and, to a lesser extent, the FREQ.RESULTS file. This helpfile describes these files, and covers some related options that affect their contents and format.
This helpfile also describes how the individual reach
contributions for each item within a combination of items
is calculated. Note, the latter was substantially improved
with version 2.23 release 6 in September, 2006.
TURF FILES This helpfile describes four additional output files that TURF can produce: REACH.SUMMARY, FREQ.SUMMARY, FULL.OUTPUT and TEMPLATE.
TURF.METHODS This shows how the reach and freq scores for a case are calclated.
TURF.TIMINGS This describes how the length of a TURF run can be estimated.
TURF.LIMITS This discusses what can and cannot be reasonably attemped.