gap (version 1.1-1)

mhtplot: Manhattan plot of p values

Description

To generate Manhattan plot of genomewide significance (p values). It could also be used for any random variable that is uniformly distributed. By default, a log10-transformation is applied. Note that with real chromosomal positions, it is also appropriate to plot and some but not all chromosomes.

It is possible to specify options such as xlab and ylim when the plot is requested for data in other context.

Usage

mhtplot(data, control=mht.control(), hcontrol=hmht.control(), ...)

Arguments

data

a data frame with three columns representing chromosome, position and p values

control

A control function named mht.control() with the following arguments,

1. type. a flag with value "p" or "l" indicating if points or lines are to be drawn.
2. usepos. a flag to use real chromosomal positions as composed to ordinal positions wi

hcontrol

A control function named hmht.control() with the following arguments,

1. data. chunk of data to be highlighted with default value NULL
2. colors. colors for annotated genes
3. yoffset. offset above the data point showing most significan

...

other options in compatible with the R plot function

Value

• The plot is shown on or saved to the appropriate device.

See Also

qqunif

Examples

# foo example
test <- matrix(c(1,1,4,1,1,6,1,10,3,2,1,5,2,2,6,2,4,8),byrow=TRUE,6)
mhtplot(test)
mhtplot(test,mht.control(logscale=FALSE))

# fake example with Affy500k data
affy <-c(40220, 41400, 33801, 32334, 32056, 31470, 25835, 27457, 22864, 28501, 26273, 
         24954, 19188, 15721, 14356, 15309, 11281, 14881, 6399, 12400, 7125, 6207)
CM <- cumsum(affy)
n.markers <- sum(affy)
n.chr <- length(affy)
test <- data.frame(chr=rep(1:n.chr,affy),pos=1:n.markers,p=runif(n.markers))

# to reduce size of the plot
# bitmap("mhtplot.bmp",res=72*5)
oldpar <- par()
par(cex=0.6)
colors <- rep(c("blue","green"),11)
# other colors, e.g.
# colors <- c("red","blue","green","cyan","yellow","gray","magenta","red","blue","green",
#             "cyan","yellow","gray","magenta","red","blue","green","cyan","yellow","gray","magenta","red")
mhtplot(test,control=mht.control(colors=colors),pch=19,bg=colors)
title("A simulated example according to EPIC-Norfolk QCed SNPs")
# dev.off()
par(oldpar)

mhtplot(test,control=mht.control(usepos=TRUE,colors=colors,gap=10000),pch=19,bg=colors)
title("Real positions with a gap of 10000 bp between chromosomes")
box()

data <- with(mhtdata,cbind(chr,pos,p))
glist <- c("IRS1","SPRY2","FTO","GRIK3","SNED1","HTR1A","MARCH3","WISP3","PPP1R3B",
         "RP1L1","FDFT1","SLC39A14","GFRA1","MC4R")
hdata <- subset(mhtdata,gene%in%glist)[c("chr","pos","p","gene")]
color <- rep(c("lightgray","gray"),11)
glen <- length(glist)
hcolor <- rep("red",glen)  
par(las=2, xpd=TRUE, cex.axis=1.8, cex=0.4)
ops <- mht.control(colors=color,yline=1.5,xline=3)
hops <- hmht.control(data=hdata,colors=hcolor)
mhtplot(data,ops,hops,pch=19)
axis(2,pos=2,at=1:16)
title("Manhattan plot with genes highlighted",cex.main=1.8)

mhtplot(data,mht.control(cutoffs=c(4,6,8,16)),pch=19)
title("A plain Manhattan plot")