assocplot {graphics} | R Documentation |
Produce a Cohen-Friendly association plot indicating deviations from independence of rows and columns in a 2-dimensional contingency table.
assocplot(x, col = c("black", "red"), space = 0.3, main = NULL, xlab = NULL, ylab = NULL)
x |
a two-dimensional contingency table in matrix form. |
col |
a character vector of length two giving the colors used for drawing positive and negative Pearson residuals, respectively. |
space |
the amount of space (as a fraction of the average rectangle width and height) left between each rectangle. |
main |
overall title for the plot. |
xlab |
a label for the x axis. Defaults to the name (if any) of
the row dimension in x . |
ylab |
a label for the y axis. Defaults to the name (if any) of
the column dimension in x . |
For a two-way contingency table, the signed contribution to Pearson's
chi^2 for cell i, j is d_{ij} = (f_{ij} - e_{ij}) / sqrt(e_{ij}),
where f_{ij} and e_{ij} are the observed and expected
counts corresponding to the cell. In the Cohen-Friendly association
plot, each cell is represented by a rectangle that has (signed) height
proportional to d_{ij} and width proportional to
sqrt(e_{ij}), so that the area of the box is
proportional to the difference in observed and expected frequencies.
The rectangles in each row are positioned relative to a baseline
indicating independence (d_{ij} = 0). If the observed frequency
of a cell is greater than the expected one, the box rises above the
baseline and is shaded in the color specified by the first element of
col
, which defaults to black; otherwise, the box falls below
the baseline and is shaded in the color specified by the second
element of col
, which defaults to red.
Cohen, A. (1980), On the graphical display of the significant components in a two-way contingency table. Communications in Statistics—Theory and Methods, A9, 1025–1041.
Friendly, M. (1992), Graphical methods for categorical data. SAS User Group International Conference Proceedings, 17, 190–200. http://www.math.yorku.ca/SCS/sugi/sugi17-paper.html
## Aggregate over sex: x <- margin.table(HairEyeColor, c(1, 2)) x assocplot(x, main = "Relation between hair and eye color")