magerr: Error bar plotting

In magicaxis: Pretty Scientific Plotting with Minor-Tick and Log Minor-Tick Support

Error bar plotting

Description

A function to add x and y error bars to plots. Low and high error bars can be generated.

Usage

magerr(x, y, xlo, ylo, xhi = xlo, yhi = ylo, corxy, length = 0.02,
col = 'black', fill = FALSE, poly = FALSE, ...)

Arguments

x	Numeric vector; x location of data.
y	Numeric vector; y location of data.
xlo	Numeric vector; error on the low side for x values. This can be positive or negative- the absolute vaue is used. If length 1, then will be repeated length(x) times.
ylo	Numeric vector; error on the low side for y values. This can be positive or negative- the absolute vaue is used. If length 1, then will be repeated length(x) times.
xhi	Numeric vector; error on the high side for x values. This can be positive or negative- the absolute vaue is used. By default this will inherit the xlo value. If length 1, then will be repeated length(x) times.
yhi	Numeric vector; error on the high side for y values. This can be positive or negative- the absolute vaue is used. By default this will inherit the ylo value. If length 1, then will be repeated length(x) times.
corxy	Numeric vector; if this parameter exists then error ellipses will be drawn instead of error bars. It takes the value of the sigma_x sigma_y correlation, i.e. corxy=covxy/(xlo*ylo). If length 1, then will be repeated length(x) times.
length	Numeric vector; length of error bar ends. If length 1, then will be repeated length(x) times.
col	Either the colour of the error bars or the outline colour of the error ellipses. If length 1, then will be repeated length(x) times.
fill	Logical; if TRUE then the error ellipses will be filled, if FALSE then only the border will be drawn.
poly	Logical; is FALSE then error bars or ellipses will be drawn, if TRUE then approximate error polygon will be shown instead.
...	Further arguments to be passed to the arrows / draw.ellipse / polygon functions used to draw the error bars / error ellipses (corxy not missing) / error polygon (poly=TRUE).

Details

Note that with poly=TRUE the x values are used igoring any error terms, and the point value y errors are used to define the limits of the polygon, with straight lines joining the points. The col option is used to fill the polygon with a colour (so the default black is probably not a great choice). The polygon function takes the argument border (parsed by dots from the magerr function) to colour the outer lines, so for a more subtle error polygon you might want to use col=lightgrey, border=NA, where NA means no outer border lines are drawn.

Value

Called for the side effect of plotting error bars.

Author(s)

Aaron Robotham

See Also

magplot, magaxis, maglab, magmap, magrun, arrows, draw.ellipse, polygon

Examples

# Basic x and y errors added to plot
temp=cbind(x=runif(10),y=runif(10),xerr=runif(10,0.05,0.2),yerr=runif(10,0.1,0.3),
corxy=runif(10,-1,1))
magplot(temp[,1:2])
magerr(x=temp[,1],y=temp[,2],xlo=temp[,3],ylo=temp[,4])
# Example of errors on plots wityh log axes
magplot(temp[,1:2],log='xy')
magerr(x=temp[,1],y=temp[,2],xlo=temp[,3],ylo=temp[,4])

#Example of error ellipses

magplot(temp[,1:2])
magerr(x=temp[,1],y=temp[,2],xlo=temp[,3],ylo=temp[,4])
magerr(x=temp[,1],y=temp[,2],xlo=temp[,3],ylo=temp[,4],corxy=temp[,5])

magicaxis documentation built on Sept. 2, 2025, 9:09 a.m.