 • seriograph() produces a Ford diagram highlighting the relationships between rows and columns.

• eppm() computes for each cell of a numeric matrix the positive difference from the column mean percentage.

## Usage

seriograph(object, ...)

eppm(object, ...)

# S4 method for matrix
eppm(object)

# S4 method for data.frame
eppm(object)

# S4 method for matrix
seriograph(
object,
weights = FALSE,
fill = "darkgrey",
border = NA,
axes = TRUE,
...
)

# S4 method for data.frame
seriograph(
object,
weights = FALSE,
fill = "darkgrey",
border = NA,
axes = TRUE,
...
)

## Arguments

object

A $$m \times p$$ numeric matrix or data.frame of count data (absolute frequencies giving the number of individuals for each category, i.e. a contingency table).

...

Currently not used.

weights

A logical scalar: should the row sums be displayed?

fill

The color for filling the bars.

border

The color to draw the borders.

axes

A logical scalar: should axes be drawn on the plot? It will omit labels where they would abut or overlap previously drawn labels.

## Value

• seriograph() is called it for its side-effects: it results in a graphic being displayed (invisibly returns object).

• eppm() returns a numeric matrix.

## Details

The positive difference from the column mean percentage (in french "écart positif au pourcentage moyen", EPPM) represents a deviation from the situation of statistical independence. As independence can be interpreted as the absence of relationships between types and the chronological order of the assemblages, EPPM is a useful tool to explore significance of relationship between rows and columns related to seriation (Desachy 2004).

seriograph() superimposes the frequencies (grey) and EPPM values (black) for each row-column pair in a Ford diagram.

Desachy, B. (2004). Le sériographe EPPM: un outil informatisé de sériation graphique pour tableaux de comptages. Revue archéologique de Picardie, 3(1), 39-56. doi:10.3406/pica.2004.2396 .