TURF.RESULTS

This TURF helpfile describes the REACH.RESULTS and FREQ.RESULTS files which are produced by the TURF command. This section was last updated on Sept 14, 2006.

The REACH.RESULTS file shows the combinations that had the best reach scores; the FREQ.RESULTS file shows the combinations that had the best freq scores.

Most TURF runs will request a reach.results file.

The REACH.RESULTS file

REACH.RESULTS rrr 300

optional output P-STAT system file. This file holds the combinations with the best REACH values. They are in descending order on REACH. Within ties on reach, the combinations are in descending order on FREQ.

The item names in a combination are ordered by the reach contribution that each in turn adds.

The default is to write the 100 best combinations for each size. If an integer like 300 follows the file name, that many are written for each size.

Each combination will take from 1 to 5 lines, as determined by the REACH.DETAILS identifier, described below. The default is two lines: one for the item names, the second for the cumulative reach for each successive item.

The names of the variables in the REACH.RESULTS file itself are these. Note, some (or all) of the initial 6 can be dropped by using the OMIT identifier, described below.

1. SIZE: the combination size.
   
   
2. RANK: the rank within size.
   
   
3. REACH: the reach value for the combination.
   
   
4. PCT.REACHED: the percent of usable cases reached by the combination. The usable cases are the cases with no invalid data. This includes cases with no responses whatsoever.
   
   
5. PCT.OF.MAX.REACH: the percent of active cases reached by the combination. An active case is a usable case that has at least one positive response; other cases cannot possibly be reached.
   
   
6. FREQ: the freq value for the combination.
   
   
7. ITEM.1, ITEM.2, ITEM.3, etc: These variables contain the names of the items that make up a combination. The item names are ordered by their contribution to the reach score. I.e., the name appearing under ITEM.1 is the 'best' item in the combination.
   
   If sizes 6 and 8 are both being done, the file will have item.1 through item.8. The results for size 6 will have blanks for item.7 and item.8.
   

The REACH.RESULTS file: the items in a combination are ordered by importance

Suppose 6 items, AA, BB, CC, DD, EE and FF, make up a combination about to be written to the reach.results file.

Before writing them, they are reordered so that the leftmost item is the one with the highest individual reach. The next item shown has, when paired with the leftmost item, the largest 2-item reach score, and so on.

The reordering is done in this manner.

FIRST PHASE: Find the smallest number of items (taken from the combination now being re-ordered) that gets a a nonzero reach, and determine the best item or group of items at that size. In the simple case, that will be just one item.

When the reach threshold is 3 and there are no item or response weights, for example, we will not get a nonzero reach until groups of three are tried. We take the best of all possible groups of three.

SECOND PHASE: We now have one or more items as the beginning items for the reordered combination. If more remain, try each one with the beginning items, and add the item that adds the most to the reach count. Repeat this step until all items are added.

Suppose we are reordering a combination of 6 items, AA, BB, CC, DD, EE and FF. When we started by trying each one by itself and that produced nonzero reaches, we have a single best item and we have a reach score for it. That is simple and obvious to show in the reach results file.

          For example:  DD    CC    EE    AA    FF    BB
                        43    62    71    78    81    82

However, suppose nonzero reaches did not begin until groups of three were tried. If BB, DD and EE were the best such group, they are shown in input order, with the reach score for the group under the last one. The symbol --> appears under the initial items in that group.

           For example:  BB    DD    EE    CC    FF    AA
                         -->   -->   37    55    61    64

This shows that no reaches occurred until groups of three items were tried, and that BB-DD-EE were the best of all 3-item groups.

Since AA, CC and FF remained, BB-DD-EE-AA was tried, then BB-DD-EE-CC, then BB-DD-EE-FF. The output shows that CC added more than the others, bringing the reach for those four items up to 55, and so on.

Note: the above procedure was adapted in Sept,06 in version 2.23 rev 6. The previous code was fine in the simple case, but was unsatisfactory when, for example, the reach threshold was other than one.

The REACH.RESULTS file: TURF can be flummoxed by small, carefully constructed data sets

It should be noted that selecting the best two items in a stepwise manner is not quite the same as selecting the best two by trying all possible pairs.

Suppose we have a file of 14 cases. Again, there are 4 items: AA, BB, CC and DD. We would like to find the 'best' two items.

     AA reaches cases 1-10,
     BB reaches cases 11-13,
     CC reaches cases 1- 5 and 11-12,
     DD reaches cases 6-10 and 13-14.

The stepwise approach selects AA and, having AA in hand, adds BB to get its best two items. They have a reach of 13.

A non-stepwise approach tries all combinations of size 2 and would select CC and DD. They have a reach of 14.

The TURF command uses a stepwise procedure only in the REACH.RESULTS (and FREQ.RESULTS) reordering; otherwise all runs are done trying every possible combination of the size being analyzed.

The REACH.RESULTS file: using OMIT to drop some (or all) of the first 6 statistics

OMIT size pct.of.max.reach,

The default is for the reach.results and freq.results files to have six numeric values before the items appear. These are:

SIZE

RANK

REACH

PCT.REACHED

PCT.OF.MAX.REACH

FREQ

An OMIT phrase can be used to drop any number of them, including all of them. This may reduce the number of print passes to see it. One OMIT phrase applied to both results files.

OMIT, in other words, can be used to cause a better looking listing.

The REACH.RESULTS file using REACH.DETAILS to select which (if any) extra lines should be written for each combination.

REACH.DETAILS cumulative.pct,

When a reach.results file is written, the items within each combination are ordered by their reach contribution within the combination. This is always done.

In addition, an extra line is written for each group which shows the cumulative reach as each item is added. That is the default, but it can be changed.

As many as four extra lines are possible:

1. cumulative, the increasing reach as each succesive item is added. This is the default.
   
2. separate, which has the additional reach provided by each successive item.
   
3. cumulative.pct, the percent of the cases reached as each itme is added.
   
4. separate.pct, the additional percent of cases reached by each successive item.
   

REACH.DETAILS can be followed by:

1. NONE by itself, no line are written.
2. ALL by itself, 4 lines are written.
3. one or more of CUMULATIVE, SEPARATE, CUMULATIVE.PCT and SEPARATE.PCT. The requested lines would be written.

The FREQ.RESULTS file

FREQ.RESULTS fff 500,

optional output P-STAT system file. This file holds the combinations with the best FREQ values. They are in descending order on FREQ. Within ties on FREQ, the rows are in descending order on REACH.

The default is to write the 100 best combinations for each size. If an integer like 500 follows the file name, that many are written for each size.

The item names in a combination are ordered by the freq contribution that each in turn adds.

The FREQ.RESULTS file has the same variables as the REACH.RESULTS file.

The FREQ.RESULTS file: which (if any) extra lines should be written for each combination

FREQ.DETAILS cumulative.pct,

When a freq.results file is written, the items within each combination are ordered by their freq contribution within the combination. This is always done.

In addition, an extra line is written for each group which shows the cumulative freq as each item is added. That is the default, but it can be changed.

Two extra lines are possible:

1. cumulative, the increasing total freq as each succesive item is added. Default.
2. separate, which has the additional freq provided by each successive item.
   
   

FREQ.DETAILS can be followed by:

1. NONE by itself, no line are written.
2. ALL by itself, 2 lines are written.
3. one or both of CUMULATIVE and SEPARATE. The requested lines would be written.