[R] strwidth and strheight for rotated text

[Stéphane Dray]

Thanks a lot Brian,
you were completely correct. The good way to do it :


z <- rnorm(10)
x1 <- 5
y1 <- 0
label <- "Label"
cha <- paste(" ", label, " ", sep = "")
X11(height=4)
plot(z)
xusr <- par("usr")
xh <- strwidth(cha, cex = par("cex"))
yh <- strheight(cha, cex = par("cex")) * 5/3
tmp <- xh
xh <- yh/(xusr[4]-xusr[3])*par("pin")[2]
xh <- xh/ par("pin")[1] * (xusr[2]-xusr[1])
yh <- tmp/(xusr[2]-xusr[1])* par("pin")[1]
yh <- yh/ par("pin")[2] * (xusr[4]-xusr[3])
rect(x1 - xh/2, y1 - yh/2, x1 + xh/2, y1 + yh/2, col = "white")
text(x1, y1, cha, cex = par("cex"), srt = 90)


Prof Brian Ripley wrote:
> See ?par, 'cxy' for how to go from width/heights in inches to user 
> coordinates and vice versa.  You appear to have overlooked 'pin'.
>
> On Wed, 7 Nov 2007, Stéphane Dray wrote:
>
>> Dear All,
>> I would like to plot text with a box around it. I used strwidth and
>> strheight to compute the size of the box which is plotted with rect:
>>
>> z <- rnorm(10)
>>
>> # horizontal text works
>> plot(rnorm(10))
>> x1 <- 5
>> y1 <- 0
>> label <- "Label"
>> cha <- paste(" ", label, " ", sep = "")
>> xh <- strwidth(cha, cex = par("cex"))
>> yh <- strheight(cha, cex = par("cex")) * 5/3
>> rect(x1 - xh/2, y1 - yh/2, x1 + xh/2, y1 + yh/2, col = "white")
>> text(x1, y1, cha, cex = par("cex"))
>>
>> Now I would like to do the same with rotated text. I found two 
>> solutions:
>> -  modify the par("usr")
>> -  compute ratio to transform width and height computed on the unrotated
>> text.
>>
>> These two solutions work for square graphic window (e.g. X11(),
>> X11(width=3, height=3)..)
>>
>> But the two solutions does not work for rectangular windows:
>>
>> # does not works for rotated text using modif of par("usr")
>> X11(height=4)
>> plot(z)
>> x1 <- 5
>> y1 <- 0
>> xusr <- par("usr")
>> par("usr"=xusr[c(3,4,1,2)])
>> yh <- strwidth(cha, cex = par("cex"))
>> xh <- strheight(cha, cex = par("cex")) * 5/3
>> par("usr"=xusr)
>> rect(x1 - xh/2, y1 - yh/2, x1 + xh/2, y1 + yh/2, col = "white")
>> text(x1, y1, cha, cex = par("cex"), srt = 90)
>>
>> # does not works for rotated text using manual modification of xh and yh
>> X11(height=4)
>> plot(z)
>> x1 <- 5
>> y1 <- 0
>> xusr <- par("usr")
>> xh <- strwidth(cha, cex = par("cex"))
>> yh <- strheight(cha, cex = par("cex")) * 5/3
>> tmp <- yh
>> yh <- xh/(xusr[2]-xusr[1])*(xusr[4]-xusr[3])
>> xh <- tmp/(xusr[4]-xusr[3])*(xusr[2]-xusr[1])
>> rect(x1 - xh/2, y1 - yh/2, x1 + xh/2, y1 + yh/2, col = "white")
>> text(x1, y1, cha, cex = par("cex"), srt = 90)
>>
>>
>>
>> I can not understand why it does not work. Any help would be very
>> appreciated.
>>
>> > sessionInfo()
>> R version 2.6.0 (2007-10-03)
>> i686-pc-linux-gnu
>>
>> locale:
>> LC_CTYPE=fr_FR.UTF-8;LC_NUMERIC=C;LC_TIME=fr_FR.UTF-8;LC_COLLATE=fr_FR.UTF-8;LC_MONETARY=fr_FR.UTF-8;LC_MESSAGES=fr_FR.UTF-8;LC_PAPER=fr_FR.UTF-8;LC_NAME=C;LC_ADDRESS=C;LC_TELEPHONE=C;LC_MEASUREMENT=fr_FR.UTF-8;LC_IDENTIFICATION=C 
>>
>>
>>
>>
>> Thanks in Advance,
>> Cheers.
>>
>>
>>
>


-- 
Stéphane DRAY (dray at biomserv.univ-lyon1.fr )
Laboratoire BBE-CNRS-UMR-5558, Univ. C. Bernard - Lyon I
43, Bd du 11 Novembre 1918, 69622 Villeurbanne Cedex, France
Tel: 33 4 72 43 27 57       Fax: 33 4 72 43 13 88
http://biomserv.univ-lyon1.fr/~dray/