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20 lines
649 B
R
20 lines
649 B
R
#####################################
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############# trapz #################
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#####################################
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trapz <- function(x, y) {
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## Description:
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## Performs a trapezoidal integration (approximate numerical integration
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## of the area under the curve defined by the x and y coordinate pairs.
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## See Wikipedia for more info on trapezoidal integration.
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## Usage:
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## trapz(x, y)
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## Arguments:
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## x: vector (of length n)
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## y: vector (of length n)
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## Return value:
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## vector of length (n - 1)
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#
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idx <- 2:length(x)
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return (as.double((x[idx] - x[idx - 1]) * (y[idx] + y[idx - 1])) / 2)
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}
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