Peakpvoigt2

Purpose

Outputs a pseudo-Voigt function, Jacobian, and Hessian for a given set of input parameters and axis.

Synopsis

[y,y1,y2] = peakpvoigt2(x,ax);

Description

Given a 4-element vector of parameters (x) and a vector of independent variables e.g. a wavelength or frequency axis (ax), PEAKPVOIGT2 outputs a pseudo-voigt peak (y). If more than one output is requested, it also outputs the Jacobian (y1) and Hessian (y2). Derivatives are with respect to the parameters and are evaluated at (x). This function is called by PEAKFUNCTION.

Inputs

• x = 4 element vector with parameters

• x(1) = coefficient ,

• x(2) = mean ,

• x(3) = spread , and

• x(4) = fraction Gaussian .

• ax = vector of independent variables e.g. a wavelength or frequency axis with elements , .

Outputs

• y = vector with the Lorentzian function, .

• y1 = matrix of the Jacobian of evaluated at (x).

• y2 = matrix of the Hessian of evaluated at (x).

Algorithm

The function is

• y = 1 by N vector with the pseudo-voigt function evaluated at (x) and given by

z = p-x(2)
y = x(1)*( x(4)*exp(-4*ln(2)*z.^2/x(3)^2) + (1-x(4))*x(3)^2./(x(3)^2+z.^2) )

Examples

%Make a single known peak

ax = 0:0.1:100;

y = peakpvoigt2([2 51 8 0.5],ax)

plot(ax,y)

See Also

peakfunction, peakgaussian, peaklorentzian, peakpvoigt1, peakstruct