I searched the archives and did not find a solution, so I pose this question to
those well-versed in the use of plotmath and expressions.
I have a list of strings in an external CSV file which I wish to use sometimes
as plot axis labels and sometimes as plot titles. These strings combine
plaintext and a few mathematical expressions (Greek letters, subscripts).
Moreover, I sometimes need to concatenate other plaintext with these strings.
Thus far I have written my string list to look like this:
"X translation ("*mu*"m)"
"Rotation ("*degree*")"
"Mean ("*mu*"m)"
"Vb1-Vb2 "*(Omega)
H[2]O "Used"
Max P
# Defects
I read in the strings, and use one at a time in the variable
"parmlabel".
I have another variable called "testlabel" which I also need to
concatenate, and can be things like "distance" or "E-test".
Sometimes I also concatenate another variable "oplabel" when the
variable "op" is not zero-length.
I have kludged a solution using this function:
expr.label<-function(title=""){
## single quote the character # so that it is not interpreted as a comment
parmlabel<-gsub("#","'#'",cfg$parmlabel[icfg])
## make sure that a string like "Vb1-Vb2" is not interpreted as
subtraction
text1<-gsub("-","*'-'*",testlabel)
## if need to prepend title test, do that, and make multiple spaces single
if(nchar(title)) text1<-paste(gsub(" ","
",title)," ",testlabel,sep="")
## substitute to avoid interpretation of "for"
text1<-gsub("for","f*or",text1,fixed=TRUE)
## substitute ~ for spaces to avoid errors in parsing
text1<-gsub(" ","~",text1,fixed=TRUE)
## see if we have a parsable expression
text2<-try(parse(text=parmlabel),silent=TRUE)
## if not parsable then concatenate another way
if(class(text2)=="try-error" | length(text2)==0){
text2<-gsub(" ","~",parmlabel)
exprtitle<-paste(text1,text2,sep="~")
} else{
exprtitle<-paste('"',text1,'~"*',text2,sep='')
}
exprtitle<-paste(text1,text2,sep="~")
## if the variable op is not zero-length, then use oplabel
if(nchar(op)>1) exprtitle=paste(exprtitle,'~',gsub('
','~',oplabel),sep="")
return(exprtitle)
}
As an example:
> parmlabel<-'"Vb1-Vb2 "*(Omega)'
> testlabel<-'E-test'
> op<-'dev lab'
> oplabel<-'Development Lab'
> expr.label("SPC Chart for")
I then use exprtitle in:
plot(1:10,title= if(plotnum==1) parse(text=exprtitle) else NULL)
However:
this code seems convoluted and ungainly
I don't always get the results I want
Any suggestions?
Leif Kirschenbaum
Senior Yield Engineer
Reflectivity, Inc.
(408) 737-8100 x307
leif at reflectivity.com
