Hi Folks,
I don't think I'm up to implementing a function for
drawing French Curves, as requested by "dream".
However, the discussion about it took me back so vividly
to the old days that, paranormally, I felt once again
the urge to ascertain magnitudes as it used to be, and
should be, done.
I have therefore implemented, and hereby donate to the
R community, a new function vernier() which implements
the Venier Caliper.
Its definition is below. Test it by entering
vernier(pi+sqrt(.182))
By following the instructions you should find that
the result is
x = 3 Units + 5 Tenths + 7 Hundredths
which is good enough for anyone. It generalises to
non-decimal Vernier Calipers (change the default "n=10",
but I leave it to you to work out how to deal with the
texts).
All best wishes,
Ted.
vernier <- function(x,n=10) {
dS<-1/n; dV<-((n-1)/n)*dS
U<-floor(x)
plot(c(0,U+2,U+2,0,0),c(0,0,2,2,0),type="l",
main="Vernier
Caliper",xlab="",ylab="",axes=FALSE)
lines(c(0,U+2),c(1.5,1.5))
for(i in (0:(U+2))){lines(c(i,i),c(1.5,1.6))}
for(i in (0:4)){lines(U+5*dS*c(i,i),c(1.5,1.575))}
for(i in (0:20)){lines(U+dS*c(i,i),c(1.5,1.55))}
lines(c(x,x),c(1.5,1.0))
for(i in (1:20)){if(x+i*dV<=U+2){lines(x+c(i,i)*dV,c(1.5,1.45))}}
text(x+1/10,1.25,"Vernier",adj=0)
text(x+1/10,1.75,"Standard",adj=0)
arrows(0,1.25,x,1.25)
arrows(x,1.25,0,1.25)
text(x/2,1.15,"x")
text(0.25,0.75,
"1: Count the main divisions of Standard Scale for Units",adj=0)
text(0.25,0.60,
"2: Count the minor divisions of Standard Scale for Tenths",adj=0)
text(0.25,0.45,
"3: Count Vernier divisions till coincidence for Hundredths",adj=0)
}
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E-Mail: (Ted Harding) <Ted.Harding at nessie.mcc.ac.uk>
Fax-to-email: +44 (0)870 094 0861
Date: 01-Apr-05 Time: 21:31:39
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