hello,
i make here my suggeestion of a Ternary Plot as a RSM.
cleber


################################################

trimage <- function(f){
[[elided Yahoo spam]]
t1 = length(x)
im = aux = numeric(0)
for( i in seq( 1, t1, by = 2 ) ){
     #idx = seq( t1**2, i*t1, by = -t1 ) - ((t1 - i):0)
     idx = seq( i*t1, t1**2, by = t1 ) - (i-1)
     im = c(im, aux, idx, aux )
     aux = c(aux, NA)
     }
z =  outer(X=x, Y=y, FUN=f)
return( matrix(z[im],nr=t1) )
}
##############################################

# dataset of mail: Francesco --- june,4

a <- c(0.1, 0.5, 0.5, 0.6, 0.2,        0, 0, 0.004166667, 0.45)
b <- c(0.75,0.5,0,0.1,0.2,0.951612903,0.918103448,0.7875,0.45)
c <- c(0.15,0,0.5,0.3,0.6,0.048387097,0.081896552,0.208333333,0.1)
d <- c(500,2324.90,2551.44,1244.50, 551.22,-644.20,-377.17,-100, 2493.04)
df<- data.frame (a, b, c, d)

reg <- lm( d ~ -1 + a*b*c )
mod <- gsub(":","*", paste( coef(reg), '*', names(coef(reg)), collapse=' 
+ '))

spf <- function( a,b,c ){eval(parse(text=mod))}
f1 <- function(a,b){ c=1-a-b; return( spf(a,b,c) ) }
zmat <- trimage(f1)

windows(w=4.5, h=4.5)
par(mar=c(0,0,0,0), pty='s', xaxt='n', yaxt='n', bty='n' )
image(zmat)










Em 19/12/2013 13:38, Nicholas Hamilton escreveu:
> Dear Walmes,
>
> I wanted to mention that I have just published on CRAN, a package for R,
> for the plotting of ternary diagrams.
>
> It is based off ggplot2, which is highly regarded, and, my website can be
> viewed at www.ggtern.com, including many examples, specifically including a
> case study at the following address:
>
> http://ggtern.com/case-study-zirconia-alumina-silica/
>
> Hope you find it of value.
>
> Best Regards,
>
> Nicholas Hamilton
> School of Materials Science and Engineering
> Univesity of New South Wales
> Sydney Australia
>
>


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