Mean velocity profile from DOF and plot ascii

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tahoser
Posts: 5
Joined: Thu Mar 05, 2009 3:25 pm

Mean velocity profile from DOF and plot ascii

Postby tahoser » Tue Aug 03, 2010 8:26 am

Hi Marc,

I have got a question about the new otpion DOF in dinver. I would like to use it to average my velocity profile and I would like to know if you use a certain weighting to do it and what it is form.

I also have a question about the report I obtained when I used dinver with command line. Actually, I would like to plot the dispersion curve obtained and I want to compar it with a dispersion curve that I have in ascii format and I do not know how to plot it with the dispersion curve from the result, that I plot with gpdcreport and gpprofile.

Thank you for your help

Best regards
Estelle

admin
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Postby admin » Tue Aug 03, 2010 2:30 pm

Hi Estelle,

The DOF option is required for the importance sampling (see http://www.geopsy.org/wiki/index.php/Importance_sampling). It generates a population of models that follows a probability law defined by a neighborhood approximation (see Sambridge 1999 for theoretical details). The approximation of the a posteriori probability density function is based on the misfit values computed during the "normal" inversion process (see formula from Sambridge 1999 which includes a DOF).

DOF is the number of statistically independent data samples, or the rank of the covariance matrix of the data set.

There is no explicit "weighting" (I do not like the term) in this process. At the end you get an ensemble of models which density is directly linked to the probability function used to generate it. Computing an average is of the resulting parameters is statistically correct (but do not forget the standard deviations and other cross terms).

To plot a custom curve saved in a two-column file:

Code: Select all

cat mycurve.txt | figue -curve


To save this result in .layer file (equivalent to graphical menu actions):

Code: Select all

cat mycurve.txt | figue -c -e my.layer -f LAYER


To plot fundamental dispersion curves from a .report file with a maximum misfit of 1:

Code: Select all

gpdcreport my.report -m 1 -pR 0 | figue -many-curve -palette my.pal

Option -pal is not mandatory, if not present a default palette is built.

Finally to plot your initial curve on top of the dispersion curves of the report and to save as a .png image file with a low resolution valid for slide presentations (other formats available):

Code: Select all

gpdcreport my.report -m 1 -pR 0 | figue -many-curve -palette my.pal -append-layer my.layer -e my.png -dpi 100 -f PNG


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