[Ifeffit] General question

[Bruce Ravel]

On 10/13/2016 05:17 PM, Dimitar Popmintchev wrote:
> I would like to ask, after a fit (in Artemis) which column in the output
> file gives the uncertainty for peaks position dR (R+/-dR  i.e. 3+/-0.02
> Angstroms)  ?

Error bars are not propagated in Artemis currently.  That's something 
you, the user, has to do using the math expression that relates your 
variable(s) to the delta R in question.

The simplest common case is one where you have

    guess delr = 0

then later, for some path,

    reff   = 3.0
    deltaR = delr

In that case, delr is varied and the path length is 3.0 + delr.

Propagating the uncertainty in this case is trivial:

    delta( 3.0 + delr) = delta(3.0) + delta(delr)

3.0 is a constant, so the error bar in the path length is the same as 
the error bar in the variable.

HTH,
B



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