4.49 sddsexpfit

• description: sddsexpfit does exponential fits to a single column of an SDDS file as a function of another column, the independent variable. The fitting function is

  where x is the independent variable, C is the constant term, F is the factor, and R is the rate.

• examples:
  sddsexpfit vacDecay.sdds -columns=Time,Pressure vacDecay.fit  
  sddsexpfit vacDecay.sdds -columns=Time,Pressure \  
    vacDecay.fit -clue=decays -tolerance=1e-12  
    

• synopsis:
  sddsexpfit [-pipe=[input][,output]] [inputFile] [outputFile]  
    [-columns=xName,yName] [-tolerance=value]  
    [-clue={grows|decays}] [-guess=constant,factor,rate]  
    [-verbosity=integer] [-fullOutput]  
    

• switches:
  • -pipe=[input][,output] — The standard SDDS Toolkit pipe option.
  • -columns=xName,yName — Specifies the names of the independent and dependent columns of data.
  • -tolerance=value — Specifies how close sddsexpfit will attempt to come to the optimum fit in terms of the mean squared residual. The default is 10^-8.
  • -clue={grows|decays} — Helps sddsexpfit decide whether the data is a decaying or growing exponential, i.e., whether R is negative or positive. If sddsexpfit is having trouble, this often helps.
  • -guess=constant,factor,rate — Gives sddsexpfit a starting point for each of the three fit parameters.
  • -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 — Requests informational printouts during fitting. A larger integer produces more output.
• files: inputFile contains the columns of data to be fit. If inputFile contains multiple pages, each page is fit separately. outputFile has columns containing the independent variable data and the corresponding values of the fit, named by appending the string Fit to the name of the dependent variable. If -fullOutput is given, outputFile includes a column with the dependent values and the residual (dependent values minus fit values), named by appending Residual to the dependent variable name. outputFile contains four parameters: expfitConstant, expfitFactor, expfitRate, and expfitRmsResidual. The first three parameters are respectively C, F, and R from the above equation. The last is the rms residual of the fit.
• see also:
  • Data for Examples
  • sddspfit()
  • sddsgfit()
  • sddsoutlier()
• author: M. Borland, ANL/APS.