El Mac 9/El Mac 9.iso/Shareware/Demos/Igor Demo Pro/1 PutContentsIn Igor Pro Folder/WaveMetrics Procedures/Analysis/WMFitFunctions

Text File | 1994-02-18 | 7.5 KB | 297 lines | [TEXT/IGR0]

| WMFitFunctions v1.1    - 11/1/93
|
| These functions were contributed or suggested by Igor users.
| We have renamed them so that the last digit(s) is the number of coefficients.
| For example, power_3 has three coefficients, w[0], w[1], and w[2].
| When describing the equation, we use Kn for w[n] because it's a little easier to read.
|
| To use one of these functions, copy it and paste into your procedure window rather
| than opening or #including this entire file; it will shorten your compile time a little.

| POLYNOMIAL FUNCTIONS
| y = K0 +K1*x (Use this to hold K0 or K1 constant; built-in line fit can't do that)
Function/D lineHold_ff2(w,x)
    Wave/D w;Variable/D x

    return w[0]+w[1]*x
End

| y = K0 +K1*x + K2*x^2 (Use this to hold K0 … K2 constant; built-in poly fit can't do that)
Function/D poly_ff3(w,x)
    Wave/D w;Variable/D x

    return w[0]+(w[1]+ w[2]*x)*x
End

| y = K0 +K1*x + K2*x^2 +K3*x^3  (Use this to hold K0 … K3 constant; built-in poly fit can't do that)
Function/D poly_ff4(w,x)
    Wave/D w;Variable/D x

    return w[0]+(w[1]+(w[2]+w[3]*x)*x)*x
End

| y = K0 +K1*x + K2*x^2 +K3*x^3 +K4*x^4  (Use this to hold K0 … K4 constant; built-in poly fit can't do that)
Function/D poly_ff5(w,x)
    Wave/D w;Variable/D x

    return w[0]+ (w[1]+ (w[2]+(w[3]+w[4]*x)*x)*x)*x
End


| EXPONENTIAL FUNCTIONS

| y= K0 + x**K1, x > 0
Function/D power_ff2(w,x)
    Wave/D w;Variable/D x

    return w[0] + x^w[1]
End

| y= K0 + K1*x**K2, x > 0
Function/D power_ff3(w,x)
    Wave/D w;Variable/D x

    return w[0] + w[1]*(x^w[2])
End
| y= K0 + K1**x
Function/D k1RaisedX_ff2(w,x)
    Wave/D w;Variable/D x

    return w[0] + w[1]^x
End

| y= K0 + K1**x
Function/D k2RaisedX_3(w,x)
    Wave/D w;Variable/D x

    return w[0] + w[1]*w[2]^x
End

| y = K0 + K1*exp(x/K2) + K3*exp(x/K4), similar to dblexp
Function/D dblexpInv_ff5(w,x)
    Wave/D w;Variable/D x

    return w[0] + w[1]*exp(x/w[2]) + w[3]*exp(x/w[4])
End

| LOGARITHMIC FUNCTIONS


| y= K0 + K1*ln(x), x > 0
Function/D ln_ff2(w,x)    | NOT ln^2
    Wave/D w;Variable/D x

    return w[0] + w[1]*ln(x)
End

| y= K0 + K1*log(x), x > 0
Function/D logBaseTen_ff2(w,x)
    Wave/D w;Variable/D x

    return w[0] + w[1]*log(x)
End

| y= K0 + K1*log2(x), x > 0
Function/D logBaseTwo_ff2(w,x)
    Wave/D w;Variable/D x

    return w[0] + w[1]*ln(x)/ln(2)    | for a different base b, replace ln(2) with ln(b).
End


| SPECIAL-PURPOSE FUNCTIONS
| The following functions are classified by what they are used for,
| rather than their mathematical form.

| GEOLOGIC FUNCTIONS
| Dr. John D. Weeks
| [e-mail]
| Here are two functions we have used in stress relaxation experiments
| studying rock friction.  In these experiments a load is applied, and the
| loading piston is held at a constant position.  Any creep of the sample
| results in decaying stress as the (relatively) compliant loading piston
| changes length.  A particular function giving stress as a function of slip
| velocity (stress = c1 + c2*ln(V)) yields a velocity decay described by a
| hyperbola in time:

| y = K0 /(K1+ x)
Function/D hyperbola_ff2(w, x)    | see also kin2ndOrder_3 function
    Wave/D w; Variable/D x

    return w[0]/(w[1] + x)
End

| This function also describes the decay of rate of aftershocks after an
| earthquake.  This is probably *not* a coincidence.
|
| This decay in velocity results in the following function for decay of
| stress with time:

| y = K0 + K1*ln(K2+x)
Function/D logplus_ff3(w,x)    | NOT log+3
    Wave/D w; Variable/D x

    return w[0]+w[1]*ln(w[2]+x)
End

| KINETICS FUNCTIONS
| [e-mail] (James Wishart)
|
| y = K0 + K1/(1+K2*x)
Function/D kin2ndOrder_ff3(w, x)
     Wave/D w;Variable/D x

     return w[0] + w[1]/(1+w[2]*x)
End

| y = K0 + K1*exp(K2*x) + K3*exp(K4*x)
Function/D KinTwo1stOrder_ff5(w, x)   |Returns two first orders - this is similar to dblexp
    Wave/D w;Variable/D x

     return w[0] + w[1]*exp(w[2]*x)+ w[3]*exp(w[4]*x)
End

| y = K0 +  K1/(1+K2*x) + K3*exp(K4*x)
Function/D Kin1st2ndOrder_ff5(w, x)   |Returns second and first orders
    Wave/D w;Variable/D x

     return w[0] + w[1]/(1+w[2]*x)+ w[3]*exp(w[4]*x)
End

| y = K0  + K1*exp(K2*x) + K3*exp(K4*x) + K5*x
Function/D KinTwo1stOrderSlope_ff6(w, x)    |Returns two first orders plus slope
     Wave/D w;Variable/D x    |Slope compensates for baseline drift or
                                | a slow subsequent kinetic process

     return w[0] + w[1]*exp(w[2]*x)+ w[3]*exp(w[4]*x)+ w[5]*x
End

| y = K0  + K1*exp(K2*x) + K3*x
Function/D Kin1stOrderSlope_ff4(w, x)   |Returns first order plus slope
    Wave/D w;Variable/D x

    return w[0] + w[1]*exp(w[2]*x)+ w[3]*x
End

| y = K0  +  K1/(1+K2*x) + K3*x
Function/D Kin2ndOrderSlope_ff4(w, x)   |Returns second order plus slope
    Wave/D w;Variable/D x

     return(w[0] + w[1]/(1+w[2]*x)+ w[3]*x )
End

| BIOLOGICAL/THERMODYNAMICS FUNCTIONS
|
| Szoke Sz, Belgium
| "Szvke Sz." <[e-mail]>
|  The following equations are used in water adsorption isotherms, etc.
| their inverse (x = f(y)) could be used as growing functions of living things
Function/D adsorpA_ff2(w, x)
        Wave/D w; Variable/D x

    return ln(ln(1/x) / w[1]) / ln(w[0])
End

Function/D adsorpB_ff2(w, x)
        Wave/D w; Variable/D x

    return((-w[1] / ln(x))^(1 / w[0]))
End

Function/D adsorpC_ff2(w, x)
        Wave/D w; Variable/D x

    return((-w[1] / ln(1 - x))^(1 / w[0]))
End

Function/D adsorpD_ff2(w, x)
        Wave/D w; Variable/D x

    return(w[0] * (x / (1 - x)) + w[1])
End

Function/D adsorpE_ff2(w, x)
        Wave/D w; Variable/D x

    return(w[0] / ln(x) + w[1])
End

Function/D adsorpF_ff2(w, x)
        Wave/D w; Variable/D x

    return(w[1] * (x / (1 - x))^w[0])
End

Function/D adsorpG_ff2(w, x)
        Wave/D w; Variable/D x

    return(w[1] - w[0] * ln(1 - x))
End

Function/D adsorpG_ff7(w, x)
        Wave/D w; Variable/D x

    return(w[1] + (w[2] + w[3] * x) * (tanh(w[4] * (x - w[5])) + w[6]))
End

| temperature sensors can give Kelvin temperature versus electrical resistance as :
Function/D tempKelvinFromRes_ff4(w, Res)
    Wave/D w; Variable/D Res

    return(1/(w[0] + w[1] * (Log(Res)) + w[2] * (Log(Res))^2 + w[3] * (Log(Res))^3))
End

| SIGMOIDS
| Basic power sigmoid
|  Alan Saul <[e-mail]>
Function/D Sigmoid_ff3(w,xx)
    Wave/D w            | w[0] is saturation amplitude
                        | w[1] is exponent, should be restricted
                        | w[2] is x value at 50% of saturation
    Variable/D xx        | xx could be lots of things, e.g. contrast

    Variable/D tmp
    tmp=w[2]^w[1]+xx^w[1]
    Return w[0]*xx^w[1]/tmp
End

| This tanh function is the solution to the differential equation x'=x(1-x).
| It comes up in chemical waves or other such reaction-diffusion equations.
|  Alan Saul <[e-mail]>
Function tanh_ff3(w,xx)
    wave/D w    | w[0] is saturation amplitude
            | w[1] is slope at 50% point
            | w[2] is x value at 50% of saturation
    variable/D xx    | xx could be time, space, ...

    Return w[0]/(1+exp(-w[1]*(xx-w[2])))
End

| PEAK FUNCTIONS
| Voigt Approximation
| For w[4]==1, this is a Lorentzian, and for w[4] -> infinity it is a Gaussian.
|     (actually for w[4]>50, it is really close to a Gaussian already).
| For this function, center = w[2]
|   Full Width at Half Maximum= 2*w[3]*sqrt((2^(1/w[4])-1)*w[4])
| For a Gaussian,  FWHM = 2*w[4]*sqrt(ln(2))
| For a Lorentzian, FWHM = 2*sqrt(w[4])
| [e-mail] (Jon Tischler)
Function/D Pearson_ff5(w,x)
    Wave/D w; Variable/D x

    return w[0]+w[1] / (  1 + (x-w[2])^2/w[4]/w[3]^2  )^w[4]
End

| Difference of Gaussians
|  Alan Saul <[e-mail]>
Function/D DoG_ff4(w,xx)
    Wave/D w        | w[0] is center strength, w[1] is center width
                    | w[2] is surround strength, w[3] surround width
    Variable/D xx    | xx could be spatial position or a frequency

    Variable/D center,surround
    center=w[0]*exp(-0.5*(xx/w[1])^2)
    surround=w[2]*exp((-0.5*xx/w[3])^2)
    Return center-surround
End