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16 lines
719 B
Plaintext
16 lines
719 B
Plaintext
14 years ago
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##################################################
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################ pearson.beta ####################
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##################################################
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pearson.beta <- function(m, w) {
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# Function for calculating integral breadth, \beta, of
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# an X-ray reflection using the half-width of FWHM (w)
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# and m parameter from a Pearson fit.
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## Args: m - shape parameter from Pearson fit (numeric)
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## w - half the FWHM for the reflection (numeric)
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## **** NOTE: gamma(x) out of range for x > 171
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## Values: The integral breadth of the reflection (numeric)
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# Ref: Birkholz2006, page 96 (Eq. 3.5)
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beta <- ((pi * 2^(2 * (1 - m)) * gamma(2 * m - 1)) /
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((2^(1 / m) - 1) * (gamma(m))^2)) * w
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}
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