[R] mtext uses the typographical descender to align text

[Andreas Svensson]

Hi

The reason I use expression is to get italics. Perhaps this is possible 
some other way?

/A

Peter Dalgaard wrote:

>Andreas Svensson <andreas.svensson at bio.ntnu.no> writes:
>
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>>
>>Hello
>>
>>One sometimes (quite often really ) marvel at the choice of defaults in 
>>R's graphic engine.
>>For some obscure reason, mtext uses the typographical  descender (bottom 
>>of letters) to align text. That is: "gG" will end up slightly higher 
>>that "GG". Depending on the font, "Q" might end up higher than "O".
>>
>>(for explanation of baseline & descender see: 
>>http://www.paratype.com/help/term/terms.asp?code=88)
>>    
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><snip>
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>>mtext(expression(italic("Normal 1"))   ,1 ,  line=1, at=1)
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><snap>
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>>As the word "Higher" includes a descending letter (g), this factor name 
>>ends up higher.
>>I must say I have never encountered a software that uses the 
>>typographical descender instead of the baseline to align text .
>>
>>Does anyone know how to make R use the baseline instead? Perhaps using  
>>adj or padj? Or do I have to do something silly as adding
>>"g", col=white
>>to each mtext-line to trick R into aligning the names.
>>    
>>
>
>Notice that it only happens when plotting math expressions. Using 
>
> mtext("Normal 1"   ,1 ,  line=1, at=1,font=3)
> mtext("Higher 1 "  ,1 ,  line=1, at=2, font=3)
>etc.
>
>does not exhibit the same effect. 
>
>I suppose the idea is that math expressions can grow arbitrarily tall
>or deep, and that the design decision (wise or not) has been to align
>on the bounding box of the whole enchilada. For a workaround, if you
>do need to do it with expressions, notice the phantom() construction.
>
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