VPLX is a FORTRAN 77 program developed in the 1990’s for the calculation of variances for complex sample designs through replication. It is in the public domain and is provided here “as is” for historical purposes.
The software is available in the form of Fortran source code. A Fortran compiler (such as f77, f90, or gfortran) will be required to install VPLX.
VPLX evolved within an original syntactic design. To improve the usability of VPLX, a three-phase plan to improve the syntax began in 1997. Version 1998.09 reflects the results of the first phase of revision. It received considerable internal testing at the Census Bureau, and is the release presented here. While a beta version from the second phase of revision was produced and tested internally, it was never released, and development of VPLX ceased.
VPLX is written in FORTRAN 77, but users are not required to know Fortran. Instead, users specify the application in the VPLX language.
Currently, the VPLX language is undergoing major revision. For example, the following sample of old syntax,
subtract persons minus rooms into test if test (1-high) then _ constant 1 into overcrowded end if
is equivalent to the following new syntax,
if persons > rooms then overcrowded = 1;
As this example illustrates, the new syntax incorporates features of Fortran, the SAS language, and other computationally oriented languages.
VPLX applications are organized into a series of steps. The new syntax has been implemented in the CREATE step and the closely related REWEIGHT step. The current production version of VPLX, 1998.09, incorporates these revisions. Version 1998.09 also runs applications with CREATE or REWEIGHT steps written in the old syntax. Thus, this version is recommended to all users except PC users running Windows 3.1.
A beta version is currently undergoing testing at the Census Bureau. It incorporates revised syntax for the TRANSFORM step. It will also support older applications.
Consequently, all but Windows 3.1 users are currently encouraged to work with the production release.
VPLX has also been compiled under VAX VMS and some other environments, but only PC and UNIX versions are currently maintained on this site.