Hi David,
It's best to keep the mailing list in the loop so I'm cc-ing to R-help.
I've rethought your problem and propose a different solution.
The main problem is to create a vector of expressions to be used in
the legend.
(see https://stat.ethz.ch/pipermail/r-help/2011-February/270106.html)
tau.vals <- c(51,88,200)
types <- c("B&K UA 1404","01dB BAP 21","RION WS3")
leg <- vector("expression", 3)
for(i in 1:3) leg[i] <-
substitute(expression(
TYPE ~ group("(", tau == tauval, ")")
),
list(TYPE=types[i], tauval=tau.vals[i])
)[2]
plot(0);legend(x="topright",legend=leg)
The idea is to create an expression vector and then
fill its components appropriately. We need the second
component of the substitute call.
Peter Ehlers
On 2012-03-21 06:49, "ECOTIÈRE David (Responsable d'activité) - CETE
Est/LRPC de Strasbourg/6 Acoustique" wrote:
Well, I have some problems with this solution:
Here is my (real) code:
tau<-c(51,88,200)
types<-c("B&K UA 1404","01dB BAP 21","RION WS3")
types<-gsub(pattern=" ", replacement="~",x=types)
leg<-parse(text=paste(types,"(","tau==",tau,"min)", sep='~'))
plot(0)
legend(x="topright",legend=leg)
I've got an error after the 'parse' command :
Erreur dans parse(text = paste(types, "(", "tau==", tau, "min)", sep =
"~")) :
<text>:2:3: symbole inattendu(e)
1: B&K~UA~1404~(~tau==~51~min)
2: 01dB
^
But no error if "01dB" is replaced by "dB01" (which is not what I want
of course). It's like if it was impossible to have a letter that follows
à number.
Any idea ?
Thank you
David
Le 21/03/2012 12:57,> Peter Ehlers (par Internet) a écrit :
On 2012-03-20 06:09, "ECOTIÈRE David (Responsable d'activité) - CETE
Est/LRPC de Strasbourg/6 Acoustique" wrote:
Hi,
I'd like to make a legend with a mix of mathematical symbol (tau),
numeric variable and character variables.I have tried :
types<-c("Type 1","Type 2","Type 2")
tau<-c(1,3,2)
legend(x="topright",legend=paste(types,"tau=",expression(tau)))
but it doesn't work: the 'tau' symbol is not written in its 'symbol
style' but as 'tau'
Any (good) idea ?
Thank you in advance !
David
Does this do what you want:
types<- paste('Type', 1:3, sep='~')
mytau<- 4:6
leg<- parse(text=paste(types, "~~tau==", mytau, sep='~'))
plot(0)
legend('topright', legend=leg)
The '~' symbols generate spaces; use more if you want more spacing.
Peter Ehlers
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