descendZero: Find start and end points of a peak
In xcms: LC-MS and GC-MS Data Analysis

Description Usage Arguments Value Author(s) See Also Examples

Decends down the sides of a data peak and finds either the points greater than or equal to the zero intercept, the intercept with a given value, or the bottom of the first valley on each side.

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descendZero(y, istart = which.max(y))
descendValue(y, value, istart = which.max(y))
descendMin(y, istart = which.max(y))

`y`	numeric vector with values
`istart`	starting point for descent
`value`	numeric value to descend to

An integer vector of length 2 with the starting and ending indicies of the peak start and end points.

Colin A. Smith, csmith@scripps.edu

descendValue

normdist <- dnorm(seq(-4, 4, .1)) - .1
xcms:::descendZero(normdist)
normdist[xcms:::descendZero(normdist)]
xcms:::descendValue(normdist, .15)
normdist[xcms:::descendValue(normdist, .15)]
xcms:::descendMin(normdist)