Programmer Guide/Command Reference/EVAL/qinterp: Difference between revisions

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=====qinterp=====
Compute interploated coordinates of local peaks of a function using 2nd order interpolation.
;Usage:
:<code>qinterp(<var>dx</var><sub>scalar</sub>, <var>y</var>, <var>ip</var> {, <var>nwidth</var>})</code>
:<code>qinterp(<var>x</var><sub>vector</sub>, <var>y</var>, <var>ip</var> {, <var>nwidth</var>})</code>
:;<var>dx</var>:distance bewteen x values; <code>x[i] = ''dx'' * i</code>
:;<var>x</var>:x data vector
:;<var>y</var>:y data vector; <code>y[i] = f(x[i])</code>.
:;<var>ip</var>: a scalar or vector containing the indices of local maxima
:;<var>nwidth</var>: the width to be used for interpolation
;Result: A vector ''r'' with 2 elements (''r''[0] = xpeak, ''r[1]'' = ypeak) or a matrix with two rows (''r''[0,j] = xpeak<sub>j</sub>, ''r[1,j]'' = ypeak<sub>j</sub>) containing the interpolated coordinates of the local maxima (peaks). For the 2nd order (parabolic) interpolation the (x,y) points at ''ip-npeaks'', ''ip'' and ''ip+npeask'' are used.
;See also: [[../ipeak|ipeak]], [[../formants|formants]], [[../interp|interp]]


Lays a parabola through three points around each peak value and calculates the interpolated peak. The result is a one or two row vector or matrix.
[[../#Functions|<function list>]]
 
=====Usage:=====
 
<code>qinterp(<var>x</var>, <var>y</var>, <var>ipeak</var>, <var>nwidth</var>)</code>
 
=====Parameters:=====
 
;<var>x</var>
 
:The number for <var>x</var>[i] = i*number or the x-scale vector.
 
;<var>y</var>
 
:The data vector (function).
 
;<var>ipeak</var>
 
:The indices of the peak values or the center of the interpolation.
 
;<var>nwidth</var>
 
:The width of the interpolation. The default is <code>1</code>.
 
=====Return Type:=====
 
vector or matrix
 
=====Result:=====
 
row 1 = xpeak[]
 
row 2 = ypeak[]

Latest revision as of 11:34, 21 April 2011

Compute interploated coordinates of local peaks of a function using 2nd order interpolation.

Usage
qinterp(dxscalar, y, ip {, nwidth})
qinterp(xvector, y, ip {, nwidth})
dx
distance bewteen x values; x[i] = dx * i
x
x data vector
y
y data vector; y[i] = f(x[i]).
ip
a scalar or vector containing the indices of local maxima
nwidth
the width to be used for interpolation
Result
A vector r with 2 elements (r[0] = xpeak, r[1] = ypeak) or a matrix with two rows (r[0,j] = xpeakj, r[1,j] = ypeakj) containing the interpolated coordinates of the local maxima (peaks). For the 2nd order (parabolic) interpolation the (x,y) points at ip-npeaks, ip and ip+npeask are used.
See also
ipeak, formants, interp

<function list>

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