After the best fit is obtained, the confidence limits on two parameters can be obtained by running search_grid. This task calculates a grid of values for a given input model. The task will also calculate the absolute minimum [within the limits of the grid or the limits from the input model spectrum, whichever is larger], and use it to draw the contours ( + ).
In the simplest case the user can hit <cr> at the first few prompts. Then search_grid will select the last dataset used (from pkgpars), will use the best fit from the last run of fit (the null string ``'' at the model prompt will always select the best fit from the _prd.tab file), and will place the results in a _grd.tab file with the same root as the observed file. A grid will be built around those values, incrementing out to delta (provided by the user) in nx steps in the x dimension and ny steps in the y dimension (nx and ny provided by the user). search_grid will return values, a on the grid points, and a true minimum (which will coincide with the central grid point in this simple case).
input files: rp90_prd.tab; rp90_obs.tab
output file: rp90_a_grd.tab
xs> search_grid Performing a grid search. observed spectrum [root_obs.tab] = (rp90): <cr> # input data from rp90_obs.tab model descriptor [null --> last best fit]: <cr> # The best fit # parameters are from rp90_prd.tab root name for output file [root_grd.tab]: rp90_a # output is rp90_a_grd.tab. Root changed # because you will probably want to repeat this with different parameters
The best-fit model parameters (from previous fit) will be listed on the screen.
Please choose the grid axes: model component number for the first axis (1): <cr> first axis parameter (norm|index|temp|galacticNh|intrinsicNh): temp half range of first axis parameter: 0.5 number of steps in the first axis (1:): 10 model component number for the second axis (1): 2 second axis parameter (norm|index|temp|galacticNh|intrinsicNh): temp half range of second axis parameter: 0.5 number of steps in the second axis (1:): 10
The best-fit parameters from this current grid of fits will be listed on the screen.
The output file is in table format, and can be listed with the tables.ttools task tprint.