[R] puzzled with plotmath for matrix indices

[Claudia Beleites]

On 01/20/2011 02:11 PM, Uwe Ligges wrote:
>
>
> On 20.01.2011 14:08, Claudia Beleites wrote:
>> Gerrit,
>>
>> thanks & viele Grüße nach Oberhessen :-)
>>
>>>> plot (1, 1, ylab = expression (Z[list(i,i)]))
>> though that cannot be evaluated, either (due to [ not knowing what to do
>> with an index list)
>
>
> Works for me with a recent R version.
Sorry, my comment wasn't clear: sure it produces the desired output, what I 
meant is:
 > Z
      [,1] [,2]
[1,]    1    3
[2,]    2    4
 > i <- 2
 > eval (expression (Z[list(i,i)]))
Error in Z[list(i, i)] : invalid subscript type 'list'

whereas:
 > eval (expression (Z[i,i]))
[1] 4

(and of course all the text-based solutions also lack the beauty of the 
expression actually meaning in R what the output looks like)

>> for future searches: probably the easiest cheat is, of course,
>> plot (1, 1, ylab = expression (Z["i, i"]))
>
> which is less convenient since you could not replace i by a dynamically
> calculated number, for example.
good point.

Thanks, I learn a lot here :-)

Claudia

-- 
Claudia Beleites
Dipartimento dei Materiali e delle Risorse Naturali
Università degli Studi di Trieste
Via Alfonso Valerio 6/a
I-34127 Trieste

phone: +39 0 40 5 58-37 68
email: cbeleites at units.it