I was wondering how I can plot the positive infinity sign and -Infinity sign in plot?
Here is my R code (with no success):
plot(1, ty ='n', ann = F, xlim = c(-4, 6), ylim = c(-3.5, 1.5) )
text(c(-4, 6 ), rep(1, 2), c( bquote(- infinity ), bquote(infinity ) ) )
?plotmath starts
If the text argument to one of the text-drawing functions (text,
mtext, axis, legend) in R is an expression, the argument is
interpreted as a mathematical expression and the output will be
formatted according to TeX-like rules.
and the labels parameter of text is documented as
a character vector or expression specifying the text to be written. An
attempt is made to coerce other language objects (names and calls) to
expressions, and vectors and other classed objects to character
vectors by as.character.
(emphasis mine). bquote does not actually return an expression (the R class, not the concept), but a language object (a call, specifically). This is causing two problems:
Because R can't handle a vector of calls, c does not actually create a vector, but instead coerces the result to a list, akin to how c(sum, mean) is coerced to a list, and
While text would coerce the call returned from bquote itself to an expression (which would get parsed properly), it coerces the list to a character vector, which does not get interpreted according to plotmath.
You could coerce the list of calls produced with c and bquote explicitly with as.expression, but it's quicker to just call expression directly and avoid bquote altogether:
plot(1, ty ='n', ann = F, xlim = c(-4, 6), ylim = c(-3.5, 1.5))
text(c(-4, 6 ), rep(1, 2), expression(-infinity, infinity))
As an end note, c actually does work on multiple expressions—sort of—in that c(expression(-infinity), expression(infinity)) returns expression(-infinity, infinity). Unlike bquote, which has two named parameters, expression takes ... though, so it's easier to just call it once with multiple inputs.
Try:
text(c(-4, 6 ), rep(1, 2), c( bquote("- \U221E"), bquote("\U221E") ) )
Related
I am trying to create a piecewise function using R. I am having trouble with my plot function
a <- function(x){
ifelse(( x <-1),0,ifelse((-1<x & x<2),(x^3+1)/9ifelse((x>2),1,NA)))
}
plot(a,xlim=c(-5,5), ylim = c(-4, 7), col = "red")
I am not sure if I never created my function properly or if there is something wrong with the way that I have plotted it. The piecewise function is a little confusing because it's a straight line of 1 and 0 at its intervals and from -1 to 2 it's a weird function.
There are two typos in your function; one is tricky.
(1) missing a comma before the third ifelse (this is probably a cut-and-paste error); (2) in x<(-1), you need parentheses (or at least a space) so R doesn't think you're assigning the value 1 to x (i.e. x <- 1).
a <- function(x) {
ifelse(( x <(-1)),0,ifelse((-1<x & x<2),(x^3+1)/9,
ifelse((x>2),1,NA)))
}
plot(a,xlim=c(-5,5), ylim = c(-4, 7), col = "red")
I would like to add formatted text to a plot (title, axes labels, legend, etc.). A standard solution would be e.g.
plot(1, 1, ylab=substitute(lambda[1]))
where the y-axis label will be the greek letter λ with subscript 1. That is what I want but unfortunatelly it is hard-wired. I would like it to be flexible, i.e. to have an option to pass the text as an argument of a function. So, looking at r help, I found that the argument for substitute is an expression. So I've tried
sometext <- "lambda[1]"
e <- parse(text="sometext")
plot(1, 1, ylab=substitute(e))
But substitute ignores that e is an object an simply prints the text 'e' as the label. So instead I tried
plot(1, 1, ylab=eval(e))
which was better because eval at least evaluates the expression but the label now is literally 'lambda[1]', i.e. it is not evaluated as a greek letter λ with a subscript.
I then explicitly stated that 'e' is an expression doing
e <- expression(sometext)
and running the two previous plot commands but with the same results as before.
The closest I came to what I wanted ot achieve was doing
plot(1, 1, ylab=substitute(var[i], list(var="lambda", i=1)))
where at least the 1 is printed as a subscript but the text 'lambda' instead of the greek letter λ is printed.
Any suggestions on how can I achieve what the first command does but not hard-wired? E.g. using a string and somehow converting it to the right object so that it will be displayed properly? Thanks.
Daniel
You can pass the label as an expression like so and then use substitute inside the function:
dwat <- function(expr){
plot(1, 1, ylab = substitute(expr))
}
dwat(lambda[1])
dwat(mu[2])
If you want to pass a string instead of an expression use parse:
dwat_string <- function(string){
plot(1, 1, ylab = parse(text = string))
}
dwat_string("mu[1]")
Another option would be to use the ellipsis approach. That way you can pass an xlab or any other argument to plot:
dwat2 <- function(...){
plot(1, 1, ...)
}
dwat2(ylab = expression(lambda[1]))
you were close, checks if this works
substitute(lambda[i],list(i=i))
I'm plotting a histogram in R and I want to include a $\bar{X}$ expression in the main argument of hist and combine it with the value of a dynamically calculated variable average.
x <- rnorm(100, 1, 1)
average <- mean(x)
hist(x, main=paste("Average $\bar{X}=", average))
That SO doesn't work and I spent hours trying to get it working with an expression statement or a substitute statement, both of which I dont find a case in the examples where the value of a variable is substituted in the text.
This solution uses * to paste text and expressions and uses substitute to replace 'average' with the calculated value.
hist(x, main = substitute("Average "*bar(x)*" = "*average, list(average=average)))
Try:
hist(x, main=bquote(Average~bar(X)==.(average) )
bquote's main use is to "import-and-evaluate" named values from the global (or enclosing) environment(s) into an expression which would otherwise not be evaluating its tokens. You could add spaces to make the expression more readable but the parser ignores them:
hist(x, main=bquote( Average ~ bar(X) == .( average ) )
If you need extra spaces use multiple tilde's: ~~~
It's rather interesting to look at the code for bquote (easy since it's not hidden):
bquote
Is it possible to use a mix of character and number as plotting symbols in R legend?
plot(x=c(2,4,8),y=c(5,4,2),pch=16)
points(x=c(3,5),y=c(2,4),pch="+")
legend(7,4.5,pch=c("+",16),legend=c("A","B")) #This is the problem
Use the numerical equivalent of the "+" character:
plot(x=c(2,4,8),y=c(5,4,2),pch=16)
points(x=c(3,5),y=c(2,4),pch="+")
legend(7,4.5,pch=c(43,16),legend=c("A","B"))
There are actually numerical equivalents for all symbols!
Source: Dave Roberts
The pch code is the concatenation of the Y and X coordinates of the above plot.
For example, the + symbol is in row (Y) 4 and column (X) 3, and therefore can be drawn using pch = 43.
Example:
plot(x=c(2,4,8),y=c(5,4,2),pch=16)
points(x=c(3,5),y=c(2,4),pch="+")
legend(7,4.5,pch=c(43,16),legend=c("A","B"))
My first thought is to plot the legend twice, once to print the character symbols and once to print the numeric ones:
plot(x=c(2,4,8),y=c(5,4,2),pch=16)
points(x=c(3,5),y=c(2,4),pch="+")
legend(7,4.5,pch=c(NA,16),legend=c("A","B")) # NA means don't plot pt. character
legend(7,4.5,pch=c("+",NA),legend=c("A","B"))
NOTE: Oddly, this works in R's native graphical device (on Windows) and in pdf(), but not in bmp() or png() devices ...
I bumped to this issue several time, so I wrote a tiny function below. You can use to specify the pch value, e.g.
pch=c(15:17,s2n("|"))
String to Numeric
As noted in previous answers, you can simply add the numerical equivalent of the numeric and character symbols you want to plot.
However, just a related aside: if you want to plot larger numbers (e.g., > 100) or strings (e.g., 'ABC') as symbols, you need to use a totally different approach based on using text().
`Plot(x,y,dat,type='n') ; text(x,y,labels = c(100,'ABC')
Creating a legend in this case is more complicated, and the best approach I've ever come up with is to stack legends on top of each other and using the legend argument for both the pch symbol and the description:
pchs <- c(100,'ABC','540',sum(13+200),'SO77')
plot(1:5,1:5,type='n',xlim=c(1,5.1))
text(1:5,1:5,labels = pchs)
legend(3.5,3,legend = pchs,bty='n',title = '')
legend(3.5,3,legend = paste(strrep(' ',12),'ID#',pchs),bty='n',title='Legend')
rect(xleft = 3.7, ybottom = 1.5, xright = 5.1, ytop = 3)
This uses strrep to concatenate spaces in order to shift the text over from the "symbols", and it uses rect to retroactively fit a box around the printed legend text.
Say, I have a variable rv which has some numerical value. Now, I want to plot the value of this variable on a base plot but preceded by a nicely formatted symbol e.g., r subscript m, using expression. To write on the plot I use mtext.
However, what I get is either the value of the variable, but no nicely formatted symbol (left annotation), or a nicely formatted symbol, but not the value of the variable, but the variable name...
I tried to play around with eval, but didn't get what I wanted. Here is my code:
plot(1:10, rep(10,10), ylim=c(0,12))
rv <- 0.43
#left annotation:
mtext(paste(expression(italic(r[M])), " = ", rv), side = 1, line = -1.5, adj = 0.1)
#right annotation:
mtext(expression(paste(italic(r[M]), " = ", rv)), side = 1, line = -1.5, adj = 0.9)
This is the result:
How do i get both, nice format and value of the variable? Thanks.
btw: I know that I can get it, if I use two times mtext and play around with adj and stuff. But I would really like to get it in one call or without playing around with the position of two annotations.
The bquote function will create an expression and alow substitution of values using .(var) syntax. for your case do something like:
text( 5,1, bquote( italic(r[M]) == .(rv) ) )
Just combine what you have and plot two pieces, joined by using adj:
R> plot(1:10, rep(10,10), ylim=c(0,12))
R> text(2,12, expression(paste(italic(r[M]))), adj=1)
R> text(2,12, paste("=", rv), adj=0)