R devel - Aug 2004 - mtext adj= wrong with several las= (PR#7188)

Dear all, 

Our quite basic function mtext() does wrong adjustments in some parameter
configurations. This gets obvious when using multi line texts: There is no
way to properly adjust text perpendicular to axis 2, for example.

Best


Jens Oehlschl?gel


m <- matrix(1:9, 3)
colnames(m) <- c("several\nlines", "several\nlines",
"several\nlines")

par(mfrow=c(2,2))
barplot(m, horiz=TRUE, axes=FALSE, axisnames=FALSE, main="las=0 adj=0.5 is
fine")
mtext(colnames(m), 2, at=seq(0.5+0.2, by=1+0.2, length=3), las=0, adj=0.5)
barplot(m, horiz=TRUE, axes=FALSE, axisnames=FALSE, main="las=0 adj=1 is
different")
mtext(colnames(m), 2, at=seq(0.5+0.2, by=1+0.2, length=3), las=0, adj=1)
barplot(m, horiz=TRUE, axes=FALSE, axisnames=FALSE, main="las=1 adj=0.5 is
NOT fine")
mtext(colnames(m), 2, at=seq(0.5+0.2, by=1+0.2, length=3), las=1, adj=0.5)
barplot(m, horiz=TRUE, axes=FALSE, axisnames=FALSE, main="at las=1, adj=1
works the wrong direction", sub="no way to get adj=c(1, 0.5) with
las=1 (or
2)")
mtext(colnames(m), 2, at=seq(0.5+0.2, by=1+0.2, length=3), las=1, adj=1)
par(mfrow=c(1,1))
> version
         _              
platform i386-pc-mingw32
arch     i386           
os       mingw32        
system   i386, mingw32  
status                  
major    1              
minor    9.1            
year     2004           
month    06             
day      21             
language R   


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joehl@gmx.de wrote:
> Dear all, 
> 
> Our quite basic function mtext() does wrong adjustments in some parameter
> configurations. This gets obvious when using multi line texts: There is no
> way to properly adjust text perpendicular to axis 2, for example.
> 
> Best
> 
> 
> Jens Oehlschl?gel
> 
> 
> m <- matrix(1:9, 3)
> colnames(m) <- c("several\nlines", "several\nlines",
"several\nlines")
> 
> par(mfrow=c(2,2))
> barplot(m, horiz=TRUE, axes=FALSE, axisnames=FALSE, main="las=0
adj=0.5 is
> fine")
> mtext(colnames(m), 2, at=seq(0.5+0.2, by=1+0.2, length=3), las=0, adj=0.5)
> barplot(m, horiz=TRUE, axes=FALSE, axisnames=FALSE, main="las=0 adj=1
is
> different")
> mtext(colnames(m), 2, at=seq(0.5+0.2, by=1+0.2, length=3), las=0, adj=1)
> barplot(m, horiz=TRUE, axes=FALSE, axisnames=FALSE, main="las=1
adj=0.5 is
> NOT fine")
> mtext(colnames(m), 2, at=seq(0.5+0.2, by=1+0.2, length=3), las=1, adj=0.5)
> barplot(m, horiz=TRUE, axes=FALSE, axisnames=FALSE, main="at las=1,
adj=1
> works the wrong direction", sub="no way to get adj=c(1, 0.5) with
las=1 (or
> 2)")
> mtext(colnames(m), 2, at=seq(0.5+0.2, by=1+0.2, length=3), las=1, adj=1)
> par(mfrow=c(1,1))
> 
Left / right adjustemnt seems to be perfectly OK.
The thing that matters is centering "several lines" to the specified 
("at=") location.
In fact, mtext() is not centering but bottom-aligning by adding a 
negative distance that looks OK for one line in the default font size, 
but not in most other cases.

Hence this is the same as Paul Murrell's PR#1659 ("mtext() alignment of
perpendicular text"). Fixing this, and/or improving mtext()'s
"adj"
argument to accept 2 dimensions is desirable, but might be not that 
easy... I'll take a look during the next days, but nothing promised.

Uwe Ligges


>>version
> 
>          _              
> platform i386-pc-mingw32
> arch     i386           
> os       mingw32        
> system   i386, mingw32  
> status                  
> major    1              
> minor    9.1            
> year     2004           
> month    06             
> day      21             
> language R   
> 
>

Hi Uwe,

Thanks for your mail.

I see it different: yes, Left / right adjustemnt seems to be perfectly OK.
But at axis 1 with las=1, it's not Left / right adjustement what is needed
here. Here the text needs to be right adjusted, and the (one) adj= par
should determine the vertical alignment. It is a bit confusing, but for
mtext, the distance to the axis is done via line= and adj= moves ALONG the
axis, whatever las= says. 

I agree that it would be more flexible and logical to also have the 2
element form of adj=c(horizontal, vertical) here, but I fear that this
creates a lot of incompatibilities with existing code and with S+.

Best


Jens

> Left / right adjustemnt seems to be perfectly OK.
> The thing that matters is centering "several lines" to the
specified
> ("at=") location.
> In fact, mtext() is not centering but bottom-aligning by adding a 
> negative distance that looks OK for one line in the default font size, 
> but not in most other cases.
> 
> Hence this is the same as Paul Murrell's PR#1659 ("mtext()
alignment of
> perpendicular text"). Fixing this, and/or improving mtext()'s
"adj"
> argument to accept 2 dimensions is desirable, but might be not that 
> easy... I'll take a look during the next days, but nothing promised.
--

> No, adj moves not always along the axis:
No, not yet. But mtext logically is oriented relative to its axis. And it
should behave consistently relative to its axis. 

Whichever solution is choosen finally, I think it is important, that the
default parametrisation will handle multi-line labels such that they are
centered around at= and aligned at line=, whatever side= and las= are
choosen. Beeing forced to tweak with adj= / padj= depending on side= / laswould
be very impractical. This "requirement" is easily fullfilled with
default adj=0.5 if we have mtext's adj= always move along the axis. With a
adj= / padj= solution, different defaults would be needed for the different
combinations of side= and las=.

How does it S+?

Best


Jens


# Thats my problem
txt <- "This are\nfour lines\nof some\nrubish"
y <- barplot(x, axes=FALSE, axisnames=FALSE, horiz=TRUE)
# axis doesn't align it properly
axis(2, label=rep(txt, 5), at=y, las=2, adj=0)
# and no mtext parameters give vertically centered and right adjusted text
mtext(rep(txt, 5), side=2, line=1, at=y, las=2, adj=0)


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