On Thursday, 02 August 2018 12:58:24 Patrick Dupre wrote:
> Hello,
>
> I have data with error bars on x and y.
> To fit them properly, i.e., by weighting the data, I need to convert
> the x error bar in y error bar.
> To do this I need to calculate the derivative of the fitting function.
> To make it right I need to calculate this derivative at each iteration and
> then to calculate the new error bars.
> It possible to do it with gnuplot?
Gnuplot can handle data with separate error estimates on x and y.
>From the documentation in "help fit"
A few shorthands for the `errors` qualifier are available:
`yerrors` (for fits with 1 column of independent variable), and
`zerrors` (for the general case) are all equivalent to `errors z`,
indicating that there is a single extra column with errors of the
dependent variable.
`xyerrors`, for the case of 1 independent variable, indicates that there
are two extra columns, with errors of both the independent and the
dependent variable. In this case the errors on x and y are treated by
Orear's effective variance method.
There is a worked example of use in the fit demo.
Ethan
> Thank.
>
> ===========================================================================
> Patrick DUPRÉ | | email: pd...@gm...
> Laboratoire de Physico-Chimie de l'Atmosphère | |
> Université du Littoral-Côte d'Opale | |
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