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Two of the fitting methods svdfit and curvefit also allow the user to specify his own fit function through loading (i.e. compiling) a user's private program into IDL after the loading of ez_fit. Examples of compiling linear and non-linear fit functions are given in the last section of this document.
The ez_fit package can be plugged into any other IDL program. Currently it can be accessed directly from the data viewer or catcher.
If a user need to implement a curve fitting which is not currently supported by ez_fit, he can load his own fit program (the user has to make sure that the file name and the fit function used is unique to IDL program) and then select the SVDFIT or CURVEFIT method. Examples are given below in the last section. For detail information about SVDFIT or CURVEFIT method, please refer the RSI's IDL reference manual.
Fit Method Fit Function
------------------------------------------------------------
COMFIT
EXPONENTIAL Y = a0 * a1^x + a2
GEOMETRIC Y = a0 * x^a1 + a2
GOMPERTZ Y = a0 * a1^(a2*x) + a3
HYPERBOLIC Y = 1./(a0 + a1*x)
LOGISTIC Y = 1./(a0 * a1^x + a2)
LOGSQUARE Y = a0 + a1*alog10(x) + a2 * alog10(x)^2
CURVEFIT Non-linear least square fit with weight
Default: 'FUNCT'
FUNCT = A0 * exp( -Z^2 / 2 ) + A3 + A4 * X + A5 * X^2
Z = (X - A1) / A2
Note: the user can substitute the 'FUNCT' by his
own fit function in CURVEFIT
LADFIT Y = A + Bx
LINFIT Y = A + Bx minimize chi-square
POLYFIT PY = A0 + A1*x + A2*x^2 + ...
POLYFITWFIT Y = A0 + A1*x + A2*x^2 + ... weighted
SVDFIT Least square fit with weight
Default
Y = A0 + A1*X + A2*X^2 + ...
SVDLEG
P0(X) = 1
P1(X) = X
P2(X) = (3 * X^2 - 1)/2
P3(X) = (5 * X^3 - 3 * X) / 2
...
Pn(X) = ((2n - 1)* X * Pn-1(X) - (n-1) * Pn-2(X)) / n
Default: 'MYFUNCT'
Y = A0 + A1 * sin(2*X)/X + A2 * cos(4*X)^2
Note: the user can substitute the 'MYFUNCT' by his
own fitting function in SVDFIT
GAUSSFIT F(x) = A0*EXP(-z^2/2) + A3 + A4*x + A5*x^2
z=(x-A1)/A2
A0 = Peak
A1 = Mean
A2 = Sigma
LORENTZFIT F(X) = A0 * A2^2 / ((X-A1)^2 + A2^2)
A0 = Peak
A1 = Mean
A2 = FWHM/2
The complete program package of ez_fit consists of following files:
ezfit - Unix script file auto starts viewer_startup.pro - IDL startup file used by ezfit script os.init - Operating system configuration file plot1d.pro - General purpose multi-line 1D plot package ez_fit.pro - General purpose curve-fitting packageThe ezfit and viewer_startup.pro are specially written for the solaris/sun UNIX system for easy startup of ez_fit. For the W95 system, the IDLDE's file preferences dialog should be used to set up the startup file and environment.
The operating system configuration file is defined in os.init. The current setting works for the UNIX and W95 operating systems. It is assumed that for the UNIX operating system the ez_fit is installed under the $EPICS_EXTENSIONS/bin/$HOST_ARCH directory; for W95, the ez_fit is installed under the C:\IDL\VIEWER2.2 directory, or use the same EPICS file structure as for UNIX.
The automatic and easy to use curve fitting package ez_fit.pro can be plugged into any IDL program as long as the $EPICS_EXTENSIONS/bin/$HOST_ARCH directory is in user's IDL search path and the environment variable IDL_PATH is defined before invoking IDL. On UNIX,
setenv EPICS_EXTENSIONS /usr/local/epics/extensions setenv IDL_PATH $EPICS_EXTENSIONS/bin/$HOST_ARCH:$IDL_PATH
$ ezfitTo access ez_fit from the IDL prompt within the IDL session is given below:
IDL> .run ez_fit IDL> ez_fit [,Xarray=x,Yarray=y] [,Im=im] [,Group=group]Please refer EZ_FIT for the detailed commands syntax description. Ez_fit accepts X,Y input variables either directly from the keyword Xarray, Yarray on the command line or through reading data from an input file (as described in next section).
X holds the vector values of the independent variable. If 1D data to be loaded, then Y holds the array of all dependent variables. If 2D image to be loaded, then Yarray should hold the second independent variable Y vector, and IM should hold the 2D image array.
At the end of each fitting calculation both the plot window and the tabulated text window will pop up showing the detail calculated results. The fitting plot window is re-adjustable by the mouse. A user can easily generate results for various fit methods and compare results from different fitting methods at his finger tip.
The Xarray(N) contains N values of independent variable X. The Yarray(N,M) contains M dependent variables, and for each dependent variable it contains the N values corresponding to the N X values.
The Xarray(N) contains N values of the first independent variable X. The Yarray(M) contains M values of the second independent variable Y. The IM(N,M) contains the 2D variable as function of X and Y, it gives the Z value corresponding to pair of X,Y values.
The READASCII routine returns the corresponding Xarray, and Yarray based on the user selection on the read ascii dialog. The first column read in will be treated as the independent variable, the remaining columns read in will be treated as the corresponding dependent variables.
When the data is loaded in from the input file, the dependent variables will be shown as a 2D image, a user has to first select the curve number to be fitted by clicking the display image area. If none is selected by the user then the very first vector from the dependent array will be assumed.
GetData->VectorX VectorY VectorYz VectorZx 2DImage VectorX - draw the X vector vs Index (1D input only) VectorY - draw the Y vector vs X vector (1D input only) VectorYz - draw the YZ vs X (2D input only) VectorZx - draw the ZX vs Y (2D input only) 2DImage - draw the Z value as 2D TV image (2D input only)
Curve Fit->COMFIT ->EXPONENTIAL GEOMETRIC GOMPERTZ HYPERBOLIC LOGISTIC LOGSQUARE CURVEFIT GAUSSFIT LADFIT LINFIT LORENTZFIT POLYFIT POLYFITWFIT SVDFIT Multi Fit->REGRESS (not implemented yet) LORENTZIAN
The private function to be fit must be written as an IDL function and compiled prior to calling SVDFIT or CURVEFIT.
The private function MYFUNCT2 to be fit accepts two scalar values : X and M. X is the independent variable, and M is the number of coefficients in the fit function. It must return an M-element vector containing the basis functions. See the Example program given below.
The routine GET_SVDFIT_MYFUNCT is required by ez_fit to print out the fit function on plot and tabulated text output windows.
FUNCTION myfunct2,X,M
; X : independent variable names
; M : number of terms defined in this function this must be consistant
; with the return terms by this function
;
Y = [ [1.0], [sin(2*x)], [cos(4*x)^2], [cos(6*x)^4] , [x *sin(x)], [x], [x*x]]
nterm = n_elements(Y)
if M ne nterm then $
res=dialog_message('For myfunct the NTERMS must be '+string(nterm), $
/info,title='FITTING Info')
return, Y
END
PRO get_svdfit_myfunct,fname,expres
ffname = strlowcase(fname)
if ffname eq 'myfunct2' then begin
expres='Function Name Used: MYFUNCT2'
expres=[expres,'Y = A0 + A1 * sin(2*x) + A2 * cos(4*x)^2 + A3 * sin(6*x)
^4 + A4 *x*sin(x) + A5 *x + A6*x^2']
end
END
In IDL ez_fit main window, select the
1. Load data into ez_fit
2. Select the curve to be fit
3. Pops up the SVDFIT Setup dialog by select: Curve Fit->SVDFIT
4. Use Cntl^C and carriage return keys to interrupt ez_fit
and then move mouse into main ez_fit window to get the
IDL prompt
5. Load 'test.pro' into ez_fit by
IDL> .run test1
IDL> retall
IDL> xmanager
6. Move mouse into SVDFIT Setup dialog window to update fields
Function_Name: myfunct2
NTERMS : 7
Press 'Accept' button
The private routine FUNCT2 specifies the non-linear function to be fit must accept values of X, A, and returns F, PDER. Where X(NPOINT) is the vector of input independent variable X, A(NTERMS) is the vector of fitting coefficients, F(NPOINT) returns the dependent function values at X, and PDER(NPOINT,NTERMS) return array of corresponding derivatives of F.
The routine GET_CURVEFIT_FUNCT_PVT is required for printing out fit function on plot and tabulated text output windows.
PRO FUNCT2,X,A,F,PDER
; F = A(0)*EXP(-Z^2/2) + A(3)
; Z = (X-A(1))/A(2)
;
ON_ERROR,2 ;Return to caller if an error occurs
NTERMS = 4
if n_elements(A) ne NTERMS then begin
res = dialog_message('Number of fitting terms must be'+ $
string(NTERMS),/Error)
return
end
if A[2] ne 0.0 then Z = (X-A[1])/A[2] $ ;GET Z
else z= 10.
EZ = EXP(-Z^2/2.)*(ABS(Z) LE 7.) ;IGNORE SMALL TERMS
F = A[0]*EZ + A[3] ;FUNCTIONS.
IF N_PARAMS(0) LT 3 THEN RETURN ;NEED PARTIAL?
;
PDER = FLTARR(N_ELEMENTS(X),4) ;init ARRAY.
PDER[0,0] = EZ ;COMPUTE PARTIALS
if A[2] ne 0. then PDER[0,1] = A[0] * EZ * Z/A[2]
PDER[0,2] = PDER[*,1] * Z
PDER[*,3] = 1.
RETURN
END
PRO get_curvefit_funct_pvt,fname,expres
ffname = strlowcase(fname)
if ffname eq 'funct2' then begin
expres='F(X) = A0 * exp( -Z^2 / 2 ) + A3 ,'
expres=[expres,' Z = (X - A1) / A2' ]
return
end
END
In IDL ez_fit main window, select the
1. Load data into ez_fit
2. Select the curve to be fit
3. Pops up the CURVEFIT Setup dialog by select: Curve Fit->CURVEFIT
4. Use Cntl^C and carriage return keys to interrupt ez_fit
and then move mouse into main ez_fit window to get the
IDL prompt
5. Load 'test2.pro' into ez_fit by
IDL> .run test2
IDL> retall
IDL> xmanager
6. Move mouse into CURVEFIT Setup dialog window to update fields
Procedure_Name: funct2
Initial Fitting Coefficients (comma separated)
2.,1.,1.,1.
Press 'Accept' button
Note:
Initial Fitting Coefficients are required only
for privatly defined routine.
The number of coefficient entered must be the same as the
terms defined in funct2, they must be separated by
comma.