collect.absolute.energy: Find the region around the peak value that yields a...
In landmarkacoustics/SoundPoints-R: an R version of the SoundPoints algorithm

Description Usage Arguments Details Value Author(s) See Also Examples

View source: R/collect.absolute.energy.R

finds the max value of a spectrum, then spreads out from that peak until it has determined a region whose area meets a fixed sum. Given the same sum, a low peak will yield a broader region than a high one.

1	collect.absolute.energy(spk, desired.sum)

`spk`	a vector that corresponds to a peak trace.
`desired.sum`	the area under the curve that you are looking for

this function assumes all of spk >= 0, and will perform oddly if any values are negative.

a vector with three entries:

`lo`	the index of the beginning of the region (inclusive)
`hi`	the index of the end of the region (inclusive)
`total`	the sum of the heights within the region

Benjamin N. Taft ben.taft@landmarkacoustics.com

spectrum collect.energy

##---- Should be DIRECTLY executable !! ----
##-- ==>  Define data, use random,
##--	or do  help(data=index)  for the standard data sets.

## The function is currently defined as
function (spk, desired.sum) 
{
    total <- max(spk)
    N <- length(spk)
    lo <- hi <- match(total, spk)[1]
    while (total < desired.sum) {
        action.case <- switch(1 + 2 * (is.na(lo) || lo < 2 || 
            spk[lo - 1] < 0) + (is.na(hi) || is.na(spk[hi + 1]) || 
            spk[hi + 1] < 0), ifelse(spk[lo - 1] < spk[hi + 1], 
            1, 2), 1, 2, 3)
        if (action.case == 1) {
            lo <- lo - 1
            total <- total + spk[lo]
        }
        else if (action.case == 2) {
            hi <- hi + 1
            total <- total + spk[hi]
        }
        else {
            break
        }
    }
    if (is.na(lo) || lo < 1) 
        lo <- 1
    if (is.na(hi) || hi > N) 
        hi <- N
    return(c(lo, hi, total))
  }