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Diffstat (limited to 'pkg/xtools/doc/extrema.hlp')
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diff --git a/pkg/xtools/doc/extrema.hlp b/pkg/xtools/doc/extrema.hlp new file mode 100644 index 00000000..cea82502 --- /dev/null +++ b/pkg/xtools/doc/extrema.hlp @@ -0,0 +1,27 @@ +.help extrema Dec83 xtools +.ih +NAME +extrema -- find the extrema in an array of x and y points +.ih +SYNOPSIS +.nf +nextrema = extrema (x, y, curvature, npts, dx) + +real x[npts], y[npts] # Input data points and output extrema +real curvature[npts] # 2nd deriv. of cubic spline at extrema +int npts # Number of input data points +real dx # Precision of extrema positions +.fi +.ih +DESCRIPTION +The input data points are fitted with a cubic interpolation spline. The +spline is then searched for points where the first derivative changes sign. +The minimum step size of this search is controlled by the parameter dx. +The positions of these extrema are returned in the x array, the value of the +spline at the extrema are returned in the y array, and the curvature or +second derivative of the spline at the extrema are returned in the +curvature array. The function returns the number of extrema found. +.ih +SEE ALSO +xtools.peaks +.endhelp |