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United States Department of Agriculture

Agricultural Research Service

Research Project: WATER QUALITY IMPROVEMENT FROM MANAGEMENT PRACTICES IN AGRICULTURAL WATERSHEDS Title: A macro for producing graphs used in assessing a spectrum

Author
item Meek, David

Submitted to: Midwest SAS Users Group Annual Meeting
Publication Type: Proceedings
Publication Acceptance Date: July 1, 2007
Publication Date: October 30, 2007
Citation: Meek, D.W. 2007. A macro for producing graphs used in assessing a spectrum. Proceedings of Midwest SAS Users Group Annual Meeting. October 28-30, 2007, Des Moines, Iowa. Paper D2 (CD-ROM).

Technical Abstract: This paper is intended for those familiar with the discrete Fourier transform and PROC SPECTRA from SAS/ETS®1. The procedure is called through a macro and the output variables are used to develop three diagnostic graphs and a montage. The first graph displays the log10 of the spectra, a Hanning weight interpolation of the spectra, and the 95% confidence bands of the spectra as a function of the log10 of the frequency. The second graph is an overlay of two related plots. The first plot displays the spectral density as a function of the wave number. The values are represented by black points with the ordinates plotted using the black left-hand vertical axis scale. The second plot displays the periodgram fraction as a function of the wave number. The values are represented by gray-scale needles with the ordinates plotted using the gray right-hand vertical axis scale. The third graph displays the normalized cumulative periodgram including the 95% confidence limits as a function of the wave number. A table with spectral tests is also presented. The sun spot record from 1700 -1991 is used to generate an example set of graphs and a table.

Last Modified: 7/30/2014
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