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Figure 3
Graphical representation of how changes for two different parameters affect the fit. The vertical direction shows the relative change in χ2 as the parameter value is changed. The true minimum is indicated with a vertical dashed line in red; the first derivative computation is the slope of the lines shown as red arrows. These are obtained numerically from differences in the fitting function, χ2, evaluated at two locations. In the case of one parameter, shown in blue, point p2 is close to the minimum, but the fit is very sensitive to this parameter and thus the derivative can be quite large even though no significant improvement is expected from further minimization. The second parameter, in green, point p1, is far from its minimum. Note that the deriviates for the first parameter have the opposite sign while those for the second parameter have the same sign.

Journal logoJOURNAL OF
APPLIED
CRYSTALLOGRAPHY
ISSN: 1600-5767
Volume 57| Part 1| February 2024| Pages 175-180
https://doi.org/10.1107/S1600576723011032
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