From: Santana, Mario <msantana_at_SLAC.Stanford.EDU>

Date: Tue, 15 Feb 2011 14:34:49 -0800

Date: Tue, 15 Feb 2011 14:34:49 -0800

Roger,

Let's take as an example a 2D plot. Usually you will want to plot a

3D matrix generated by USRBIN.

But the plot can only be made in 2D, so you need to choose what kind of

view you want (e.g. elevation, plain, cross section ~ X, Y, Z depending on

your reference frame). If you project the matrix on the y-z plane (X axis),

you will be plotting a {y, z} mesh in which each point {y_j, z_k} is the

average value of all the layers with the same {y_j, z_k} but different x_i

(x_1, x_2...). If you specify limits for your x axis, then FLAIR will only take

into account all the layers between your specified x range. The associated

error, for any {y_j, z_k} bin is obtained in FLAIR by calculating the

relative error of the sum of bins and dividing by the square root of the

numberof terms. In FLAIR you can actually select the 'error' box to plot the

associated relative errors. If you do so, remember to set the normalization

factor to 1 and to use a scale ranging from 0 (or close) to 100.

Anyway, in most practical cases, if your plot looks smooth (isolines are

well defined, no big traces, nor 'random' fluctuations in neighboring values)

most likely your statistical error will be acceptable. Of course, this

depends on the scale range that you use, so use good judgment.

Mario

-----Original Message-----

From: owner-fluka-discuss_at_mi.infn.it [mailto:owner-fluka-discuss_at_mi.infn.it] On Behalf Of Roger Haelg

Sent: Tuesday, February 15, 2011 6:01 AM

To: fluka-discuss_at_fluka.org

Subject: FLAIR projections and statistical error

Dear FLUKA and FLAIR experts

Could anyone explain to me what the "projection& limits" for data plots

(1d and 2d) in FLAIR exactly do with the data for plotting? The manual

does not explain this.

And what happens to the statistical error in this case? The manual says:

"WARNING errors will be underestimated, since it treats all bin values

as uncorrelated."

How can I estimate the error when using this projections and limits for

several bins? Are there different cases to be differentiated?

In the FLUKA course materials there is a table listing the statistical

errors and the usefulness of the results. Is this always related to the

statistical errors of the individual bin or is there a way to estimate

the error using projections and averaging?

Thank you very much for your help!

Regards,

Roger Haelg

Received on Wed Feb 16 2011 - 09:25:41 CET

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