**RSIC COMPUTER CODE PSR-43**

**1. NAME AND TITLE**

FLUSH: Spectral Unfolding Code -- Stepwise Regression of System Response Functions.

**2. CONTRIBUTOR**

EG&G, Los Alamos, New Mexico.

**3. CODING LANGUAGE AND COMPUTER**

Fortran IV, Machine language; CDC-6600.

**4. NATURE OF PROBLEM SOLVED**

FLUSH is a spectral unfolding procedure.

**5. METHOD OF SOLUTION**

FLUSH generates a unique solution, an envelope of solutions within a given confidence interval, and a statistical goodness-of-fit evaluation.

The solution generated is based on a series expansion of the unknown spectrum using stepwise
regression of the system response functions. If there is no prior information available, this method
generates the "best" solution possible, based purely upon the observations and the response functions.
Further, an envelope of solutions of width, dependent upon observational errors is generated. Lastly,
a statistical goodness-of-fit parameter is used to judge the quality of the unfolded solution. If prior
information is available, the addition of unobservable but plausible solutions is possible.

**6. RESTRICTIONS OR LIMITATIONS**

FLUSH is best suited to the most poorly defined and, hence, the most difficult unfolding problems.

**7. TYPICAL RUNNING TIME**

No study has been made by RSIC of typical running times for FLUSH.

**8. COMPUTER HARDWARE REQUIREMENTS**

FLUSH is operable on the CDC-6600 computer.

**9. COMPUTER SOFTWARE REQUIREMENTS**

A Fortran IV compiler is required.

**10. REFERENCES**

R. H. Beers, "Spectral Unfolding Using Stepwise Regression of System Response Functions," EGG 1183-5000 (16 April 1971).

F. Kelso, "FLUSH, CDC-6600 Computer Program," Addendum.

W. J. Dexon, "Biomedical Computer Programs," BMD02R (1968).

**11. CONTENTS OF CODE PACKAGE**

Included are the referenced documents and one (1.2MB) DOS diskette which contains the source
codes.

**12. DATE OF ABSTRACT**

December 1983.

**KEYWORD: ** UNFOLDING