R help - Feb 2002 - text that combines math expressions and numeric variables

Dear R-Help,
   I have some questions relating to math notation in text functions.  I
have studied the help for plotmath but have not figured out how to solve
two types of problems.

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.

PROBLEM 2:  How can I force a mathematical expression to move to a new
line, analogous to embedding a carriage return into the expression?  For
example,

B0 <- 20;  B1 <- .25
plot(0:100, 0:100, type="n")
text(30, 70, paste("beta.0 =", B0, "\nbeta.1 =", B1), adj=0)
#Text1
text(25, 70, "Text 1", adj=1)
text(30, 50, substitute(hat(beta)[0] == this, list(this=B0)), adj=0)
#Text2
text(30, 40, substitute(hat(beta)[1] == this, list(this=B1)), adj=0)
#Text2
text(25, 50, "Text 2", adj=1)

Text1 shows what I would like to accomplish except that I would like to
replace "beta.1" and "beta.2" with subscripted greek
symbols.  Text2 shows
what I want as output, but I have been forced to explicitly state the
Y-coordinates of the two lines of Text2.  This requires that I know the
scale on the Y-axis.  What I want is to embed a carriage return, "\n",
into the mathematical expression so that I can create a mathematical
expression on multiple lines.  Is this possible?

Any help would be much appreciated.

John Miyamoto


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John Miyamoto                           |
Department of Psychology, Box 351525    |  If ignorance is bliss,
University of Washington                |  why are so many people
Seattle, WA 98195-1525.                 |  unhappy?
Phone: 206-543-0805, Fax: 206-685-3157  |
Email: jmiyamot at u.washington.edu        |
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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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r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
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(in the "body", not the subject !)  To: r-help-request at
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