glass | R Documentation |
Sites, types, and compositions of glass samples from archaeological sites in Israel.
data(glass)
A tibble with 68 cases and 16 variables:
site at which sample was found
analysis identifier
furnace identifier
type of sample
normalized weight percent oxide of each component
Chunks of unformed glass from several furnaces found at the primary Byzantine-era site of Bet Eli'ezer, along with samples from other sites with weaker evidence of glass-making (Apollonia and Dor) and and from an Islamic-era site (Banias), were analyzed using X-ray spectrometry to determine their major components.
Baxter & Freestone (2006) used these data to illustrate log-ratio analysis.
Freestone &al (2000), Table 2.
Freestone IC, Gorin-Rosen Y, & Hughes MJ (2000) "Primary glass from Israel and the production of glass in Late Antiquity and the early Islamic period". La route du verre: Ateliers primaires et secondaires du second millénaire av. J.-C. au Moyen Âge: 65–83. https://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetail&idt=1158762
Baxter MJ & Freestone IC (2006) "Log-Ratio Compositional Data Analysis in Archaeometry". Archaeometry, 48(3): 511–531. doi: 10.1111/j.1475-4754.2006.00270.x
# subset glass data to one site and major components head(glass) glass_main <- subset( glass, Site == "Bet Eli'ezer", select = c("SiO2", "Na2O", "CaO", "Al2O3", "MgO", "K2O") ) # format as a data frame with row names glass_main <- as.data.frame(glass_main) rownames(glass_main) <- subset(glass, Site == "Bet Eli'ezer")$Anal # perform log-ratio analysis glass_lra <- lra(glass_main, compositional = TRUE, weighted = FALSE) # inspect LRA row and column coordinates head(glass_lra$row.coords) glass_lra$column.coords # inspect singular values of LRA glass_lra$sv # plot samples and measurements in a biplot biplot( x = glass_lra$row.coords %*% diag(glass_lra$sv), y = glass_lra$column.coords, xlab = "Sample (principal coord.)", ylab = "" ) mtext("Component (standard coord.)", side = 4L, line = 3L)
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