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Plot QTL peak locations

Source: R/ggplot_peaks.R
ggplot_peaks.Rd

Plot QTL peak locations (possibly with intervals) for multiple traits.

Usage

ggplot_peaks(
  peaks,
  map,
  chr = NULL,
  tick_height = 0.3,
  gap = 25,
  bgcolor = "gray90",
  altbgcolor = "gray85",
  ...
)

Arguments

peaks

Data frame such as that produced by find_peaks) containing columns chr, pos, lodindex, and lodcolumn. May also contain columns ci_lo and ci_hi, in which case intervals will be plotted.

map

Marker map, used to get chromosome lengths (and start and end positions).

chr

Selected chromosomes to plot; a vector of character strings.

tick_height

Height of tick marks at the peaks (a number between 0 and 1).

gap

Gap between chromosomes.

bgcolor

Background color for the plot.

altbgcolor

Background color for alternate chromosomes.

...

Additional graphics parameters

Value

None.

See also

find_peaks

Examples

# load qtl2 package for data and genoprob calculation
library(qtl2)

# read data
iron <- read_cross2(system.file("extdata", "iron.zip", package="qtl2"))

# insert pseudomarkers into map
map <- insert_pseudomarkers(iron$gmap, step=1)

# calculate genotype probabilities
probs <- calc_genoprob(iron, map, error_prob=0.002)

# grab phenotypes and covariates; ensure that covariates have names attribute
pheno <- iron$pheno
covar <- match(iron$covar$sex, c("f", "m")) # make numeric
names(covar) <- rownames(iron$covar)
Xcovar <- get_x_covar(iron)

# perform genome scan
out <- scan1(probs, pheno, addcovar=covar, Xcovar=Xcovar)

# find peaks above lod=3.5 (and calculate 1.5-LOD support intervals)
peaks <- find_peaks(out, map, threshold=3.5, drop=1.5)

# color peaks above 6 red; only show chromosomes with peaks
plot_peaks(peaks, map)

peaks$col <- (peaks$lod > 6)

ggplot_peaks(peaks, map[names(map) %in% peaks$chr], col = c("blue","red"),
           legend.title = "LOD > 6")