trapz_sorted: Sorted Trapezoidal Integration

In FredHutch/VISCfunctions: VISC STP/SRA functions

Sorted Trapezoidal Integration

Description

This function is a wrapper for the trapz function. It sorts the x and y values so that it is monotonically increasing along the x values. Then computes the area of a function with values y and points x. There is an optional parameter to remove any NA values so that integration can proceed by omitting the x and y values where the NA occurred.

Usage

trapz_sorted(x, y, na.rm = TRUE)

Arguments

x	A vector of numeric values representing the x-axis over which to integrate.
y	A vector of numeric values representing the y-axis.
na.rm	A logical indicating whether to remove NA values from both x and y values.

Details

The points (x, 0) and (x, y) are taken as vertices of a polygon. The area is computed using the trapezoid rule for approximation the definite integral of the function.

Value

Approximated integral of the function, discretized through the points x, y, from min(x) to max(x).

Examples

set.seed(93)

# Calculate the area under the sine curve from 0 to pi:
n <- 101
x <- seq(0, pi, len = n)
y <- sin(x)
trapz_sorted(x, y)

# Calculate area under the curve for unsorted data:
x <- sample(1:n, n, replace = FALSE)
y <- runif(n, 0, 33)
trapz_sorted(x, y)

# Calculate the area without NA removal
x[10] <- NA
y[3] <- NA
# Will fail to produce a result
trapz_sorted(x, y, na.rm=FALSE)
trapz_sorted(x, y, na.rm=TRUE)

FredHutch/VISCfunctions documentation built on Oct. 14, 2024, 11:33 p.m.