The following menu is available when this option is selected:
The error bars reported after each fit and in the Write ASCII Fit
Information file are estimated from the derivatives of 
. The
statistically `exact' errors on the parameter values are the value changes
that increase by certain amounts, as discussed in Numerical Recipes
by Press et al. The option Obtain a 1d Chi-square Plot plots the
value of versus a selected parameter, thereby allowing you to see
the confidence regions for the parameter. The option Obtain a 2d
Chi-square Map plots the value of as a contour map versus the
values of two selected parameters, thereby depicting the joint confidence
region of the two parameters. For both options, is evaluated by
doing fits on a (1-dimensional or 2-dimensional) grid of points. For the
2-dimensional case, the number of grid points can be large, implying a
significant run-time to perform the fits. We recommend doing preliminary
2-dimensional maps with a small number of grid points in order to ``home in''
on the the confidence region.
The parameter(s) to process are selected by term number and by parameter number within the term. The term numbers are listed after the ``t'' symbol in the first column of the display, while the parameter numbers are listed in the column of the display labeled ``P''.
After the fits have been made, a point and click menu will give you the choice of percentile confidence levels (90%, 99%, 99.9%) or sigma confidence levels (1, 2, or 3 sigma). Another point and click menu will ask you how many parameters are of interest. How many parameters are of interest to you depends upon the scientific question that you are asking. As described in Numerical Recipes (Press et al.), the more parameters whose values are of interest to you, the larger the size of the confidence region.
Instead of going through the long list of model terms, you can establish a `Fit Template', which is stored in a file for latter use. After doing a fit, you can store the current model as a template with the Write Fit Template option. You can also modify a model without doing a fit with the Edit Fit Template-this enables you to create a model with no selected (`Used') terms, which is not allowed by the Fit command. You can read in a previously written fit template with the Read Fit Template. This can be done automatically with the control variable (see section 9.3) MCV_STARTUP_TEMPLATE_FILE. The fit template file is an ASCII file, so you may also edit it, as long as you don't change the format and follow the obvious coding scheme.
The option Write ASCII Fit Information writes out the details of the fit to a file. The first column of this file contains a ``parse code'' which enables programs that read this file to easily locate information. Several questions are asked to control the extent of the output to this file. The control variable MCV_ALWAYS_WA can cause this file to be automatically written after each fit.
This function fits a Gaussian line feature to a spectrum at several energy
values. Multiple fits are performed, each with a line feature added to the
model at a specific energy value for the line centroid. After performing the
model fits, a plot of as a function of energy is created, allowing
an automated way to find any candidate spectral lines with little effort
required by the user.
The Write Binary Batch Output File option writes a binary file containing detailed information about the CURRENT fit. The information is very similar to the information placed into the formatted file written by the Write ASCII Fit Information option. There are control variables (MCV_ALWAYS_WB and MCV_SUPPRESS_BATCH_OUT - see section 9.3) that can be set to cause this file to be written automatically after either every fit or after every batch fit. Each fit is written at the end of the file: if you wish to group fits in various files, you can do so by explicitly closing the current binary file via Close Binary Batch Output File. Two readers are provided in the WINGSPAN directory to read these files: read_mfit_batch.for and read_mfit_batch.pro.
Once a batch fit has been performed upon a sequence of spectra, you can save the results to a file, by issuing the Write Session command. The result will be an ASCII file which can be easily parsed for the parameter names, their values and errors, as well as chi-squares and a time history of the count rate, integrated over the selected energies.
![[image 4K]](/icons-local/batse_icon.gif){kind=icon}
BATSE Home Page
