[R] Plot symbols: How to plot (and save) a graphic symbols originating from a table

[David Winsemius]

On Jan 1, 2011, at 2:15 PM, Victor F Seabra wrote:

> Dear all,
>
> Please, I have a doubt regarding symbol plotting
> with data originating from a table.

I would say it has very little to do with the data structure and  
everything to do with the encodings, font conventions of console  
output, and the defaults for graphical devices. (I'm using a Mac in an  
English locale, and you have not provided any of the requested  
information about your setup.)
>
> Please, see below:
>
> I have a tab delimited file called table1.txt with 4 columns:
>
> ypos	animal	var1	var2
> 5	cat	gina <=  lady	gina \u2264  lady
> 7	dog	bill >= tony	bill \u2265 tony
> 9	fish	dude <= bro	dude \u2264 bro
>
> #I then load in the data to R:
> table1<-read.table("table1.txt", header=TRUE, sep="\t")
>
> #if I take a look at the table I realize that \u2264 was replaced by  
> \\u2264
> table1
>

No. You are more likely seeing how R presents what it did with \u2264  
with its default method for printing to the console. I see:

 > table1
   ypos animal          var1         var2
1    5    cat gina <=  lady gina ≤  lady
2    7    dog  bill >= tony  bill ≥ tony
3    9   fish   dude <= bro   dude ≤ bro

Subject, of course, to how emailers handle the \u2264 character.

 > str(table1)
'data.frame':	3 obs. of  4 variables:
  $ ypos  : num  5 7 9
  $ animal: Factor w/ 3 levels "cat","dog","fish": 1 2 3
  $ var1  : Factor w/ 3 levels "bill >= tony",..: 3 1 2
  $ var2  : Factor w/ 3 levels "bill ≥ tony",..: 3 1 2

> #So, if i try to plot the data
> #instead of greater/equal or lesser/equal I get
> #a text string plotted "\u2265"
> plot 
> (1:1,col="white",xlim=c(1,10),ylim=c(1,10),ylab="",axes=FALSE,xlab="")
> text(y=table1$ypos,x=2,table1$animal)
> text(y=table1$ypos,x=4,table1$var1)
> text(y=table1$ypos,x=8,table1$var2)
>
> #this can be fixed if I manually erase the extra "\" on var2
> fix(table1)

I'm confused. You are starting with a factor variable whose levels  
have some higher order numbers in the character vector, and then you  
didn't assign the results of the fix() operation to an R object. Why  
should that do _anything_?

> plot 
> (1:1,col="white",xlim=c(1,10),ylim=c(1,10),ylab="",axes=FALSE,xlab="")
> text(y=table1$ypos,x=2,table1$animal)
> text(y=table1$ypos,x=4,table1$var1)
> text(y=table1$ypos,x=8,table1$var2)
>
> #However if I save the graph to a ps file, it shows the "<=" sign as  
> "..."
> postscript("teste3.ps", width = 22, height =  
> 11.5,pointsize=24,paper="special",bg="transparent")
> plot 
> (1:1,col="white",xlim=c(1,10),ylim=c(1,10),ylab="",axes=FALSE,xlab="")
> text(y=table1$ypos,x=2,table1$animal)
> text(y=table1$ypos,x=4,table1$var1)
> text(y=table1$ypos,x=8,table1$var2)
> dev.off()
>

That must be the glyph for that number in the default font for your  
pdf device (as it is for mine once I change the width settings so it  
can be seen after conversion to pdf.)

?Encoding  # might be a useful place to start, followed by...
?Devices
?ps.options

>
> #My solution was to plot "<" or ">" instead of "<=" and ">="
> # and then plot an hifen under the "<" or the ">" sign.
> # This worked to fix both problems, but is hard to do and
> # impossible to automate (or at least very difficult)
>
> #Please, does anyone know a better approach?

To accomplish what end? You have not described what you are trying to  
actually do. Is this text supposed to be plotted inside the plotting  
area or are you going to be using it as axis labels? There is a  
variety of approaches (especially the plotmath expression option) that  
can be used depending on the ultimate objective.

?plotmath

Compare:
  plot(NULL, xlim=c(0,1), ylim=c(0,1))
  text(0.5,0.5, as.expression(as.character(table1$var2[1])) )
  text(0.5,0.6, label=expression(gina <= lady) )

> #thanks in advance
>
> Victor Faria Seabra, MD
> vseabra at uol.com.br

-- 
David Winsemius, MD
West Hartford, CT