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:**Fit an exponential decay to vacuum pressure versus time during a pumpdown:`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]**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,*outputFile*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 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.**switches:**`-pipe=[input][,output]`-- The standard SDDS Toolkit pipe option.`-columns=`-- Specifies the names of the independent and dependent columns of data.*xName*,*yName*`-tolerance=`-- Specifies how close*value*`sddsexpfit`will attempt to come to the optimum fit, in terms of the mean squared residual. The default is .`-clue={grows | decays}`-- Helps`sddsexpfit`decide whether the data is a decaying or growing exponential, i.e., whether R is negative or positive, respectively. If`sddsexpfit`is having trouble, this will often help.`-guess=`-- Gives*constant*,*factor*,*rate*`sddsexpfit`a stating 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=`-- Specifies that informational printouts are desired during fitting. A larger integer produces more output.*integer*

**see also:****author:**M. Borland, ANL/APS.