Programmer Guide/Command Reference/EVAL/ipeak

Search the function y for local peaks and return either a scalar or a vector with indices of the peak values. The result can, for example, be passed directly to qinterp() to compute the interpolated peak coordinates.

Usage

ipeak(y {, npeaks, i1, i2, nwidth, ymin})

y

data vector (the function).

npeaks

the maximum number of peaks to locate (default=1)

i1, i2

the index range to be searched (default=1,ncol(y)-1)

nwidth

the minimum width of a peak (+/-) (default=1)

ymin

the threshold; must be a scalar or a vector with the same length as y (default: no threshold)

Result

A scalar or a vector containing the indices of the located peaks.

A y value at index i is a peak if:

1. the index is in the range i1 <= i <= i2
2. y[i] is greater than the threshold ymin/ymin[i]
3. (y[i-1]+y[i+1])/2 < y[i]
4. y[i-k-1] <= y[i-k] and y[i+k+1] <= y[i+k]; with: k=0..nwidth-1