[R] Fitting of lognormal distribution to lower tail experimental data

Mattias Brännström Mattias.Brannstrom at tt.luth.se
Fri Jan 16 09:39:45 CET 2009


Hi,

I am beginner with R and need firm guidance with my problem. I have seen
some other threads discussing the subject of right censored data, but I am
not sure whether or not this problem can be regarded as such.

Data:
I have a vector with laboratory test data (strength of wood specimens,
example attached as txt-file). This data is the full sample. It is a
common view that this kind of data follows a lognormal distribution.

Background:
When fitting a distribution to the lower tail, it will usually be very
different compared to fitting the whole data. The lower tail COV is the
decisive measure in my analysis (due to resistance estimations of
buildings).

Problem:
I would like to fit a lognormal distribution to the 10%-lower tail of the
attached data.

Question:
Which function would you recommend me to use, and how to formulate it in R
using the attached data?


Best regards,
Mattias Brännström

PhD student
Luleå Technical University
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