[R] paste ?

Bill Venables venables at acland.qld.cmis.csiro.au
Tue Apr 25 08:45:06 CEST 2000

> As Peter helpfully pointed out mn was a vector, so here is the corrected 
> version:
>   bland <- function (x) #accepts two columns
> {
> mn <<- 0.5*(x[,1]+x[,2]
> diff <- x[,1]-x[,2]
> plot(mn,diff,pch=16,xlab="Mean",ylab="Difference",
> main = "Bland Altman plot",
> sub= paste("Mean = ",formatC(mean(diff),digits=3)))
> abline(h=mean(diff),lty=2)
> abline(h=mean(diff)+c(2,-2)*sqrt(var(diff)))
> }

Two small points.  The line

mn <<- 0.5*(x[,1]+x[,2])

is either a mistake, or it makes this a dangerous function for
public distribution.  ("Superassignment? Just say 'No'")

Secondly, I'm curious about the history of this kind of plot.
I've only heard it called a "Tukey mean difference" plot, (and
Trellis graphics has a function, tmd(), that does it, but no one
knows about it...).  Does anyone know who invented it?

Bill Venables.

Bill Venables,      Statistician,     CMIS Environmetrics Project
CSIRO Marine Labs, PO Box 120, Cleveland, Qld,  AUSTRALIA.   4163
Tel: +61 7 3826 7251           Email: Bill.Venables at cmis.csiro.au

Fax: +61 7 3826 7304      http://www.cmis.csiro.au/bill.venables/

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