[R] text that combines math expressions and numeric variables

[Paul Murrell]

Hi


> PROBLEM 1:  How can I create expressions that mix mathematical notation,
> numeric variables, and ordinary text.  For example,
>
> B0 <- 20;  B1 <- .25
> plot(0:100, 0:100, type="n")
> text(30, 90, substitute(hat(beta)[0] == this, list(this=B0)) , adj=0)
> #Text1
> text(25, 90, "Text 1", adj=1)
> text(30, 70, paste("beta.0 =", B0, "and beta.1 =", B1), adj=0)   #Text2
> text(25, 70, "Text 2", adj=1)
> text(30, 50, substitute(hat(beta)[0] == this + hat(beta)[1] == that,
> #Text3
>      list(this=B0, that=B1)), adj=0)
> text(25, 50, "Text 3", adj=1)
>
> Text1 plots the combination of math notation and a numeric variable but it
> does not contain ordinary text.  Text2 shows what I would like to
> accomplish, except that I would like replace "beta.1" and "beta.2" with
> subscripted greek symbols.  Text3 shows something that is almost what I
> want, except that I would like to replace the "+" symbol with "and".  I am
> also puzzled by the fact that mathematical notation plots higher on the
> Y-axis than does the corresponding text.


The vertical alignment of the mathematical annotations is wrong -- it should
be treating adj=0 as adj=c(0, 0.5).  In other words, when a vertical
adjustment is not explicitly given, it should centre vertically.  At the
moment, when a vertical adjustment is not given, it is bottom-adjusting (so
to speak) i.e,. it is treating adj=0 as adj=c(0, 0).

A work around for this is to use adj=c(0, 0.5) i.e., explicitly specify
vertical centring.

I will add a proper fix for the next R release.

I think there was a similar report about vertical alignment of mathematical
annotation on R-help recently.  Can anyone confirm/point me to that?

Paul


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