| glass {comparison} | R Documentation |
Glass composition data for seven elements from 200 glass items.
Description
These data are from Grzegorz (Greg) Zadora at the Institute of Forensic Research in Krakow, Poland. They are the log of the ratios of each element to oxygen, so logNaO is the log(10) of the Sodium to Oxygen ratio, and logAlO is the log of the Aluminium to Oxygen ratio. The instrumental method was SEM-EDX.
Usage
data(glass)
Format
a data.frame with 2400 rows and 9 columns.
- item
factor
200 levels - which item the measurements came from
- fragment
factor
4 levels - which of the four fragments from each item the observations were made upon
- logNaO
numeric
log of sodium concentration to oxygen concentration
- logMgO
numeric
log of magnesium concentration to oxygen concentration
- logAlO
numeric
log of aluminium concentration to oxygen concentration
- logSiO
numeric
log of silicon concentration to oxygen concentration
- logKO
numeric
log of potassium concentration to oxygen concentration
- logCaO
numeric
log of calcium concentration to oxygen concentration
- logFeO
numeric
log of iron concentration to oxygen concentration
Details
The item indicates the object the glass came from. The levels for each item
are unique to that item. The fragment can be considered a sub-item. When
collecting these observations Greg took a glass object, say a jam jar, he
would then break it, and extract four fragments. Each fragment would be
measured three times upon different parts of that fragment. The fragment
labels are repeated, so, for example, fragment "f1" from item "s2" has
nothing whatsoever to do with fragment "f1" from item "s101".
For two level models use item as the lower level - three level models can
use the additional information from the individual fragments.
Source
Grzegorz Zadora Institute of Forensic Research, Krakow, Poland.
References
Aitken, C.G.G. Zadora, G. & Lucy, D. (2007) A Two-Level Model for Evidence Evaluation. Journal of Forensic Sciences: 52(2); 412-419.