treegram {SSRA}

Treegram

Description

This function draws a treegram for the Takeya Semantic Structure Analysis (TSSA) and Sakai Sequential Relation Analysis (SSRA)

Usage

treegram(object, select = NULL, pos = NULL, col = NULL,
  mai = c(0.2, 0, 0.2, 0.2), print.pos = TRUE, cex.text = 0.95,
  x.factor = 1.7, x.digits = 0, y.digits = 2, y.intersp = 1.45,
  cex.legend = 0.9)

Arguments

object

requires the result object of seqtab function

select

select items to be plotted

pos

position of items on the x-axis

col

color code or name for paths

mai

numeric vector of the form c(bottom, left, top, right) which gives the margin size specified in inches

print.pos

display x/y-position as legend

cex.text

text expansion factor relative to current par("cex")

x.factor

shift factor of legend position

x.digits

decimal places of x-position

y.digits

decimal places of y-position

y.intersp

legend character interspacing factor for vertical (y) line distances

cex.legend

legend character expansion factor relative to current par("cex)

Details

An item with lower item mean is located above, and an item with higher item mean is placed below in a treegram. An arrow is drawn between two items in sequential relation, namely, from the item with higher item mean to the item with lower item mean. And two items in equal relation are linked by a dashed line.

Author(s)

Takuya Yanagida [e-mail], Keiko Sakai [e-mail]

References

Takeya, M. (1991). A new test theory: Structural analyses for educational information. Tokyo: Waseda University Press.

See Also

seqtable

Examples

# Example data based on Takeya (1991)

# Sakai Sequential Relation Analysis
# ordering assesed according to the correlation coefficient and mean difference
exdat.ssra <- SSRA(exdat, output = FALSE)
exdat.seqtab <- seqtable(exdat.ssra, output = FALSE)
treegram(exdat.seqtab)

# Select items to be plotted
exdat.ssra <- SSRA(exdat, output = FALSE)
exdat.seqtab <- seqtable(exdat.ssra, output = FALSE)
treegram(exdat.seqtab, select = c("Item2", "Item3", "Item4"))

# Define position for each item on the x-axis
exdat.ssra <- SSRA(exdat, output = FALSE)
exdat.seqtab <- seqtable(exdat.ssra, output = FALSE)
treegram(exdat.seqtab, pos = c(Item5 = 1, Item4 = 3,
                               Item3 = 5, Item2 = 2, Item1 = 4))

# Change colors for each path of an item
exdat.ssra <- SSRA(exdat, output = FALSE)
exdat.seqtab <- seqtable(exdat.ssra, output = FALSE)
treegram(exdat.seqtab,
         col = c(Item5 = "red3", Item4 = "blue3",
                 Item3 = "gray99", Item2 = "darkgreen", Item1 = "darkorange2"))