Programmer Guide/Command Reference/EVAL/ipeak: Difference between revisions
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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 [[ | 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|qinterp]]() to compute the interpolated peak coordinates. | ||
;Usage: <code>ipeak(<var>y</var> {, <var>npeaks</var>, <var>i1</var>, <var>i2</var>, <var>nwidth</var>, <var>ymin</var>})</code> | ;Usage: <code>ipeak(<var>y</var> {, <var>npeaks</var>, <var>i1</var>, <var>i2</var>, <var>nwidth</var>, <var>ymin</var>})</code> | ||
:;<var>y</var>: data vector (the function). | :;<var>y</var>: data vector (the function). | ||
| Line 9: | Line 8: | ||
:;<var>ymin</var>: the threshold; must be a scalar or a vector with the same length as ''y'' (default: no threshold) | :;<var>ymin</var>: 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. | ;Result: A scalar or a vector containing the indices of the located peaks. | ||
: | :The ''y'' value at index ''i'' is a local peak if: | ||
:# the index is in the range ''i1'' ≤ ''i'' ≤ ''i2'' | |||
:# ''y''[''i''] is greater than the threshold ''ymin''/''ymin''[''i''] | |||
:# (''y''[''i''-1]+''y''[''i''+1])/2 < ''y''[''i''] | |||
:# ''y''[''i''-''k''-1] ≤ ''y''[''i''-''k''] and ''y''[''i''+''k''+1] ≤ ''y''[''i''+''k'']; with: ''k''=0..''nwidth''-1 | |||
;See also: [[../qinterp|qinterp]], [[../formants|formants]] | |||
[[../#Functions|<function list>]] | |||
Latest revision as of 20:16, 21 April 2011
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.
- The y value at index i is a local peak if:
- the index is in the range i1 ≤ i ≤ i2
- y[i] is greater than the threshold ymin/ymin[i]
- (y[i-1]+y[i+1])/2 < y[i]
- y[i-k-1] ≤ y[i-k] and y[i+k+1] ≤ y[i+k]; with: k=0..nwidth-1
