Specifying text in a base R plot() with formatting such as italics / bold font / newline usually involves one or more of the following functions:
paste()
expression()
atop()
substitute()
italic()
Is there an intuitive explanation for the differences between these functions and when best to apply them?
What you're referring to is the plotmath syntax.
To start off, let's make it clear that for a plotmath expression to be interpreted as such, you tell R it's an "expression" and that is why you need expression().
So any time you want to use special symbols or formatting, like italic() and atop(), it's actually a part of plotmath and so you need to wrap it in an expression. eg:
plot(0, main = expression(atop(over,italic(under))))
If you've tried out ?italic or ?atop, you've probably noticed it takes you straight to the plotmath manual page, where a bunch of other functions are listed.
What about substitute() ? Well in my previous example, you'll notice I used strings directly to write 'over' and 'under', without putting them within quotes. This is because of the special expression() environment.
So if you need to put whatever is inside a variable in your text (rather than the variable name) then you put your expression inside a substitute() and give it the arguments. eg:
plot(0, main = substitute(atop(oo,italic(under))), list(oo='over2')))
Note that we don't put substitute around the expression block but replace it entirely.
Finally, where does paste() come in all this ? Well, paste is the glue (pun intended) with any text not dealt with by plotmath.
So if you need text before or after math symbols (or formatted text), you paste() things together within the expression (or substitute) environment. eg :
plot(0, main = substitute(paste("b4", atop(oo,italic(under)), aft),
list(oo='over', aft = 'after3')))
As before, if you want to paste the content of a variable, you need substitute.
And Voilà that's most of the plotmath you'll ever need!
For any other symbols, or functions, have look at ?plotmath
Related
I wanted to answer a question regarding plotmath but I failed to get my desired substitute output.
My desired output:paste("Hi", paste(italic(yes),"why not?"))
and what I get: paste("Hi", "paste(italic(yes),\"why not?\")")
text<-'paste(italic(yes),"why not?")'
text
[1] "paste(italic(yes),\"why not?\")"
noqoute_text<-noquote(text)
noqoute_text
[1] paste(italic(yes),"why not?")
sub<-substitute(paste("Hi",noqoute_text),
env=list(noqoute_text=noqoute_text))
sub
paste("Hi", "paste(italic(yes),\"why not?\")")
You're using the wrong function, use parse instead of noquote :
text<-'paste(italic(yes),"why not?")'
noquote_text <- parse(text=text)[[1]]
sub<- substitute(paste("Hi",noquote_text),env=list(noquote_text= noquote_text))
# paste("Hi", paste(italic(yes), "why not?"))
noquote just applies a class to an object of type character, with a specific print method not to show the quotes.
str(noquote("a"))
Class 'noquote' chr "a"
unclass(noquote("a"))
[1] "a"
Would you please elaborate on your answer?
In R you ought to be careful about the difference between what's in an object, and what is printed.
What noquote does is :
add "noquote" to the class attribute of the object
That's it
The code is :
function (obj)
{
if (!inherits(obj, "noquote"))
class(obj) <- c(attr(obj, "class"), "noquote")
obj
}
Then when you print it, the methods print.noquote :
Removes the class "noquote" from the object if it's there
calls print with the argument quote = FALSE
that's it
You can actually call print.noquote on a string too :
print.noquote("a")
[1] a
It does print in a similar fashion as quote(a) or substitute(a) would but it's a totally different beast.
In the code you tried, you've been substituting a string instead of a call.
For solving the question I think Moody_Mudskipperss answer works fine, but as you asked for some elaboration...
You need to be careful about different ways similar-looking things are actually stored in R, which means they behave differently.
Especially with the way plotmath handles labels, as they try to emulate the way character-strings are normally handled, but then applies its own rules. The 3 things you are mixing I think:
character() is the most familiar: just a string. Printing can be confusing when quotes etc. are escaped. The function noquote basically tells R to mark it's argument, so that quotes are not escaped.
calls are "unevaluated function-calls": it's an instruction as to what R should do, but it's not yet executed. Any errors in this call don't come up yet, and you can inspect it.
Note that a call does not have its own evironment given with it, which means a call can give different results if evaluated e.g. from within a function.
Expressions are like calls, but applied more generally, i.e. not always a function that needs to be executed. An expression can be a variable-name, but also a simple value such as "why not?". Also, expressions can consist of multiple units, like you would have with {
Different functions can convert between these classes, but sometimes functions (such as paste!) also convert unexpectedly:
noquote does not do that much useful, as Moody_Mudskipper already pointed out: it only changes the printing. But the object basically remains a character
substitute not only substitutes variables, but also converts its first argument into (most often) a call. Here, the print bites you, for when printing a call, there is no provision for special classes of its members. Try it: sub[[3]] from the question gives[1] paste(italic(yes),"why not?")
without any backslashes! Only when printing the full call the noquote-part is lost.
parse is used to transform a character to an expression. Nothing is evaluated yet, but some structure is introduced, so that you could manipulate the expression.
paste is often behaving annoyingly (although as documented), as it can only paste together character-strings. Therefore, if you feed it anything but a character, it firs calls as.character. So if you give it a call, you just get a text-line again. So in your question, even if you'd use parse, as soon as you start pasting thing together, you get the quotes again.
Finally, your problem is harder because it's using plotmaths internal logic.
That means that as soon as you try to evaluate your text, you'll probably get an error "could not find function italic" (or a more confusing error if there is a function italic defined elsewhere). When providing it in plotmath, it works because the call is only evaluated by plotmath, which will give it a nice environment, where italic works as expected.
This all means you need to treat it all as an expression or call. As long as evaluation cannot be done (as long as it's you that handles the expression, instead of plotmath) it all needs to remain an expression or call. Giving substitute a call works, but you can also emulate more closely what happens in R, with
call('paste', 'Hi', parse(text=text)[[1]])
I've learned to apply bold to a portion of the text used in a plot title using mtext() expression() and paste(). This works great if you specify the strings outright. However, in the project I'm working on now, the portion of text to be bolded needs to be obtained through a call to an element of a vector. However, the characters needed in the call syntax are interpreted by expression() and the call fails.
junk <- c("I'm Special", "You're Special")
plot(0, type="n")
mtext(expression(paste("Do you think ", bold(junk[1]),"today?")),3,2)
mtext(expression(paste("I think ", bold(junk[2]), "today.")),3,1)
Any thoughts on how to approach this? I am trying to avoid specifying the bold text directly.
bquote has a decent interface for this. You just surround the variable you want to substitute with .(). You could also use substitute with expression.
junk <- c("I'm Special", "You're Special")
plot(0, type="n")
mtext(bquote(paste("Do you think ", bold(.(junk[1])),"today?")),3,2)
mtext(bquote(paste("I think ", bold(.(junk[2])), "today.")),3,1)
I make some plots with R and use bquote because I need variables for the main of the plot. However, the main is no longer bold but I want it to be bold. I defined the main as follows:
title = bquote(atop("Empirical Pricing Kernel at Date",~.(EndDate)~"with Index Price"~.(ST)~"€"))
plot(temp, EPK, type="l", main = title)
Enddate contains "2014-08-01" as date and ST is just numeric with 9210.08.
Is there any way to make it bold with or without bquote? I'd like to find a solution with bquote because it's very convenient when using subscripts.
My problem is that I am using it in a par-plot with two plots and the other plot needs no special things in it's main. So, the main is bold. I even tried to just put bquote around it in order to get the same font size but it stayed bold.
I prefer to use what I think of as "pure plotmath" so I use tilde's instead of spaces and use no quotes. I suspect it was the leading tilde in the second argument to bquote that was throwing the error. In plotmath the tildes need something on either side: If you really need a none-displayed something you can always use phantom(0) but why bother in this case?
bquote(atop(Empirical~Pricing~Kernel~at~Date,
bold(.(EndDate))~with~Index~Price~.(ST)~"€"
) )
Test:
EndDate="2014-08-01";ST=9210.08
title = bquote(atop(Empirical~Pricing~Kernel~at~Date, bold(.(EndDate))~with~Index~Price~.(ST)~"€"))
plot(1,1, type="l", main = title)
I hope to get some help on the use of quotation marks within a string for get().
Say, I want to retrieve an element from a list
some_list <- list(element1=11,element2=22,element3=33)
naturally, I can simply reference this element through
some_list[['element1']]
However, once I use this as a string within get(), R throws this error message
get("some_list[['element1']]")
> Error in get("some_list[['element1']]") :
object 'some_list[['element1']]' not found
I cannot figure out why this is the case. get() works fine when used with strings that do not have quotation marks within them, e.g.
get("some_list")
I also tried escaping the quotation marks within the string (although I don't this I would need to since they are single quotation marks) but it does not work either.
some_list[["\'"element1"\'"]]
What am I missing.
get won't do that.
some_list[['element1']] isn't the name of an object in an R environment (in a technical sense). When you type some_list[['element1']] at the console, R parses the expression, looks up the symbol some_list and then calls the function [[. get is intended just for the symbol lookup piece of that.
(Technically, my sequence of events there probably isn't right, but I listed them that way to help make the issue clear. Really, R is just parsing the expression, and then calling [[ with arguments some_list and 'element1', and those symbols are subsequently looked up.)
The quotes have nothing to do with it. Run:
get("some_list")[['element1']]
I would like to have the title for the plot in two lines, but this does not work, why? and how can I make it work?
CVal<-1
SumEpsVal<-2
plot(1:10, main=bquote(paste("C=", .(CVal), " \n ", sum(xi), "=", .(SumEpsVal) )))
This here works:
plot(1:10, main=paste("C=1", "\n", "SumXi=2"))
I guess bquote makes something wrong... (look up ?bquote)
I tried to change environment in bqoute (the where-argument) but I don't know which environment to take.
BTW:
plot(1:10, main=bquote(paste("C=", .(CVal), "bla \n ", sum(xi), "=", .(SumEpsVal) )))
makes something crazy with the "bla".
Personally I would use mtext as already suggested. But if you really want it to be a one-liner, you can "cheat" bquote by using atop:
plot(1:10, main=
bquote(atop(paste("C=",.(CVal)), paste(sum(xi),"=",.(SumEpsVal)))))
It even aligns both lines neatly to the center.
The root issue is that plotmath does not support newlines within the
expressions to be output.
Control characters (e.g. \n) are not interpreted in character strings in plotmath,
unlike normal plotting.
You really need to create and output each line separately.
For example :
Lines <- list(bquote(paste("C=", .(CVal))),
bquote(paste(sum(xi), "=", .(SumEpsVal))))
Now output each line The text in the list is converted to expressions do.call
mtext(do.call(expression, Lines),side=3,line=0:1)
One way to achieve this is to use mtext to add an additional line under the main title as follows:
plot(1:10, main=bquote(paste("C=", .(CVal))))
mtext(bquote(paste(sum(xi), "=", .(SumEpsVal) )),side=3,line=0)
There may be a prettier solution, but perhaps this is enough for your needs.