Stata 15 help for sortseed

Title

[P] set sortseed -- Set the default seed for randomly breaking ties in sorts

Syntax

set sortseed #

Description

set sortseed specifies the seed used for the random-number generator that breaks any ties in the key values when data are sorted. This affects the commands sort and gsort, as well as any commands that use sorting as part of their computation.

Remarks

set sortseed should be used rarely. Access to the sorting seed is provided solely for those doing replication studies, where occasionally it is necessary to set the sort seed to produce numerically identical results for computations whose results may change slightly when the computations are run repeatedly. These changes are typically in the digits beyond those displayed by the command, but these might be compared nevertheless in a replication study.

The current value of sortseed can be obtained by accessing stored result r(sortseed) after issuing the command query sortseed.

Using set sortseed outside of such comparisons is strongly discouraged. Many data manipulations depend on sorts being specified fully and correctly, and setting the sorting seed can disguise logic problems in data management. For a discussion, see a posting on Statalist about this topic.

Example

Obtain the sorting seed, perform some operations which change the sort order of the data (and thus change the sorting seed), and then reset the sorting seed. . query sortseed . local origseed = r(sortseed) ...any command(s) which change the sort order of the data... . set sortseed `origseed'


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