sddsgfit

• description: sddsgfit does gaussian fits to a single column of an SDDS file as a function of another column (the independent variable). The fitting function is
  
  $$G(x) = B + H * e \frac{-(x-\mu) 2}{2 \sigma 2},$$
  
  
  where x is the independent variable, B is the baseline, H is the height, ${\rm\mu}$ is the mean, and ${\rm\sigma}$ is the width.

• examples: Fit a gaussian to a beam profile to get the rms beam size:
  sddsgfit beamProfile.sdds beamProfile.gfit -column=x,Intensity
• synopsis:
  sddsgfit [-pipe=[input][,output]] [inputFile] [outputFile] -columns=x-name,y-name[,sy-name] [-fitRange=lower,upper] [-fullOutput] [-guesses=[baseline=value][,mean=value][,height=value][,sigma=value]] [-fixValue=[baseline=value][,mean=value][,height=value][,sigma=value]] [-stepSize=factor] [-tolerance=value] [-limits=[evaluations=number][,passes=number] [-verbosity=integer]
• files: inputFile contains the columns of data to be fit. If inputFile contains multiple pages, each page of data is fit separately. outputFile has columns containing the independent variable data and the corresponding values of the fit. The name of the latter column is constructed by appending the string Fit to the name of the dependent variable. In addition, if -fullOutput is given, it includes a column with the dependent values and the residual (dependent values minus fit values). The name of the residual column is constructed by appending the string Residual to the name of the dependent variable. outputFile contains five parameters: gfitBaseline, gfitHeight, gfitMean, gfitSigma, and gfitRmsResidual. The first four parameters are respectively B, H, $\mu$, and $\sigma$ from the equation above. The last is the rms residual of the fit.

• switches:
  • -pipe=[input][,output] -- The standard SDDS Toolkit pipe option.
  • -columns=x-name,y-name -- Specifies the names of the independent and dependent columns of data.
  • -fitRange=lower,upper -- Specifies the range of independent variable values to use in the fit.
  • -guesses=[baseline=value][,mean=value][,height=value][,sigma=value] -- Gives sddsgfit a starting point for one or more parameters.
  • -fixValue=[baseline=value][,mean=value][,height=value][,sigma=value] -- Gives sddsgfit a fixed value for one or more parameters. If given, then sddsgfit will not attempt to fit the parameters in question.
  • -stepSize=factor -- Specifies the starting stepsize for optimization as a fraction of the starting values. The default is 0.01.
  • -tolerance=value -- Specifies how close sddsgfit will attempt to come to the optimum fit, in terms of the mean squared residual. The default is ${\rm 10 {-8}}$.
  • -limits=[evaluations=number][,passes=number -- Specifies limits on how many fit function evaluations and how many minimization passes will be done in the fitting. The defaults are 5000 and 100, respectively. If the fit is not converging, try increasing one or both of these. If the number of evaluations is too small, you may get warning messages about optimization failures.
  • -fullOutput -- Specifies that outputFile will contain the original dependent variable data and the fit residuals, in addition to the independent variable data and the fit values.
  • -verbosity=integer -- Specifies that informational printouts are desired during fitting. A larger integer produces more output.
• see also:
  • sddspfit
  • sddsexpfit
  • sddsoutlier
• author: M. Borland, ANL/APS.