HWTernaryPlot: Ternary plot with the Hardy-Weinberg acceptance region

In HardyWeinberg: Statistical Tests and Graphics for Hardy-Weinberg Equilibrium

Ternary plot with the Hardy-Weinberg acceptance region

Description

HWTernaryPlot is a routine that draws a ternary plot for three-way genotypic compositions (AA,AB,BB), and represents the acceptance region for different tests for Hardy-Weinberg equilibrium (HWE) in the plot. This allows for graphical testing of a large set of markers (e.g. SNPs) for HWE. The (non) significance of the test for HWE can be inferred from the position of the marker in the ternary plot. Different statistical tests for HWE can be done graphically with this routine: the ordinary chisquare test, the chisquare test with continuity correction and the Haldane's exact test.

Usage

HWTernaryPlot(X, n = NA, addmarkers = TRUE, newframe = TRUE, hwcurve = TRUE, 
vbounds = FALSE, mafbounds = FALSE, mafvalue = 0.05, axis = 0, region = 1, 
vertexlab = colnames(X), alpha = 0.05, vertex.cex = 1, pch = 19, cc = 0.5, 
markercol = "black", markerbgcol = "black", cex = 0.75, axislab = "", 
verbose = FALSE, markerlab = NULL, markerpos = NULL, mcex = 1, connect =
FALSE, curvecols = rep("black",5), signifcolour = TRUE, curtyp =
"solid", ssf = "max", pvaluetype = "selome", grid = FALSE, ...)

Arguments

X	a matrix of n genotypic compositions or counts. If it is a matrix of compositions, X should have (n rows that sum 1, and 3 columns, with the relative frequencies of AA, AB and BB respectively. Argument n should be supplied as well. If X is a matrix of raw genotypic counts, it should have 3 columns with the absolute counts of AA, AB and BB respectively. Argument n may be supplied and will be used for painting acceptance regions. If not supplied n is computed from the data in X.
n	the samples size (for a complete composition with no missing data).
addmarkers	represent markers by dots in the triangle (addmarkers=TRUE) or not (addmarkers=FALSE).
newframe	allows for plotting additional markers in an already existing ternary plot. Overplotting is achieved by setting newframe to FALSE. Setting newframe = TRUE (default) will create a new ternary plot.
hwcurve	draw the HW parabola in the plot (hwcurve=TRUE) or not (hwcurve=FALSE).
vbounds	indicate the area corresponding to expected counts > 5 (vbounds=TRUE) or not (vbounds=FALSE).
mafbounds	indicate the area corresponding to MAF < mafvalue.
mafvalue	a critical value for the minor allele frequency (MAF).
axis	draw a vertex axis 0 = no axis is drawn 1 = draw the AA axis 2 = draw the AB axis 3 = draw the BB axis
region	the type of acceptance region to be delimited in the triangle 0 = no acceptance region is drawn 1 = draw the acceptance region corresponding to a Chi-square test 2 = draw the acceptance region corresponding to a Chi-square test with continuity correction 3 = draw the acceptance region corresponding to a Chi-square test with continuity correction for D > 0 4 = draw the acceptance region corresponding to a Chi-square test with continuity correction for D < 0 5 = draw the acceptance regions for all preceding tests simultaneously 6 = draw the acceptance region corresponding to a Chi-square test with continuity correction with the upper limit for D > 0 and the lower limit for D < 0 7 = draw the acceptance region corresponding to a two-sided exact test
vertexlab	labels for the three vertices of the triangle
alpha	significance level (0.05 by default)
vertex.cex	character expansion factor for the labels of the vertices of the triangle.
pch	the plotting character used to represent the markers.
cc	value for the continuity correction parameter (0.5 by default).
markercol	vector with colours for the marker points in the triangle.
markerbgcol	vector with background colours for the marker points in the triangle.
cex	expansion factor for the marker points in the triangle.
axislab	a label to be put under the horizontal axis.
verbose	print information on the numerically found cut-points between curves of the acceptance region and the edges of the triangle.
markerlab	labels for the markers in the triangle.
markerpos	positions for the marker labels in the triangle (1,2,3 or 4).
mcex	character expansion factor for the labels of the markers in the ternary plot.
connect	connect the represented markers by a line in the ternary plot.
curvecols	a vector with four colour specifications for the different curves that can be used to delimit the HW acceptance region. E.g. curvecols=c("red", "green","blue","black","purple") will paint the Hardy-Weinberg curve red, the limits of the acceptance region for an ordinary chi-square test for HWE green, the limits of the acceptance region for a chi-square test with continuity correction when D > 0 blue and the limits of the acceptance region for a chi-square test with continuity correction when D < 0 black, and the limits of the exact acceptance region purple.
signifcolour	colour the marker points automatically according to the result of a signifance test (green markers non-siginficant, red markers significant). signifcolour only takes effect if region is set to 1, 2 or 7.
curtyp	style of the drawn curves ("dashed","solid","dotted",...)
ssf	sample size function ("max","min","mean","median",...). Indicates how the sample size for drawing acceptance regions is determined from the matrix of counts.
pvaluetype	method to compute p-values in an exact test ("dost" or "selome")
grid	draw a reference grid for genotype frequencies at (0.2,0.4,0.6,0.8)
...	other arguments passed on to the plot function (e.g. main for a main title).

Details

HWTernaryPlot automatically colours significant markers in red, and non-significant markers in green if region is set to 1, 2 or 7.

Value

minp	minimum allele frequency above which testing for HWE is appropriate (expected counts exceeding 5).
maxp	maximum allele frequency below which testing for HWE is appropriate.
inrange	number of markers in the appropriate range.
percinrange	percentage of markers in the appropriate.
nsignif	number of significant markers (only if region equals 1,2 or 7.)

Author(s)

Jan Graffelman [e-mail]

References

Graffelman, J. and Morales, J. (2008) Graphical Tests for Hardy-Weinberg Equilibrium Based on the Ternary Plot. Human Heredity 65(2):77-84.

Graffelman, J. (2015) Exploring Diallelic Genetic Markers: The HardyWeinberg Package. Journal of Statistical Software 64(3): 1-23. doi: 10.18637/jss.v064.i03.

See Also

HWChisq

Examples

n <- 100 # sample size
m <- 100 # number of markers

X <- HWData(n,m)
HWTernaryPlot(X,100,region=1,hwcurve=TRUE,vbounds=FALSE,vertex.cex=2)

HardyWeinberg documentation built on May 7, 2022, 5:05 p.m.