X-Stream Operator’s Manual
WM-OM-E Rev I 145
Histogram Parameters
fwhm Full Width at Half Maximum
Definition:
Determines the width of the largest area peak, measured between bins on either
side of the highest bin in the peak that have a population of half the highest's
population. If several peaks have an area equal to the maximum population, the
leftmost peak is used in the computation.
Description:
First, the highest population peak is identified and the height of its highest bin
(population) determined (for a discussion on how peaks are determined see the
pks parameter Description:). Next, the populations of bins to the right and left are
found, until a bin on each side is found to have a population of less than 50% of
that of the highest bin's. A line is calculated on each side, from the center point of
the first bin below the 50% population to that of the adjacent bin, towards the
highest bin. The intersection points of these lines with the 50% height value is
then determined. The length of a line connecting the intersection points is the
value for fwhm.
Example:
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