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Sometimes it is more instructive to view a plot of the fit residuals when judging whether to reject a point by hand. To view a residuals plot, type capital 'R' in the 1D fitting window. Zooming and rejection work as before. To change back from residuals mode to the actual fit values, type capital 'V' in the residuals plot window. A view of a residual plot is shown below.
In this fit, the included points are shown in green crosses, and points thrown out because of iterated deviations from the fit are shown in triangles. The fit is shown in red.
The default fitting function is a standard polynomial; using teh bac at left this may be changed to a Legendre or Chebyshev polynomial, or a bspline. Typically we do not use bsplines; these sometimes produce smaller residuals but can exhibit unphysical fluctuations from being insufficiently stiff.
The order of the fit may be changed using the "up" and "down" buttons, or pressing the lowercase "u" or "d" keys.
To delete an errant point from the fit by hand, either right click or use the 'D' key (beware of confusing 'D' and 'd' in this GUI!). A second right-click or 'D' undoes the rejection.
You may also change the sigma thresholds for automatic rejection in the text boxes at top. You need to press return in these windows to re-fit with new thresholds.
As in the x_identify GUI, you may zoom in to specific regions using 't', 'b', 'l', and 'r', or alternatively 's' and 's' to define a window.
Sometimes it is more instructive to view a plot of the fit residuals when judging whether to reject a point by hand. To view a residuals plot, type capital 'R' in the 1D fitting window. Zooming and rejection work as before. To change back from residuals mode to the actual fit values, type capital 'V' in the residuals plot window. A view of a residual plot is shown below.
