[R] plotmath: how to use greek symbols in expression(integral(f(tau)*dtau, 0, t))?

[David Winsemius]

On Oct 4, 2010, at 10:11 AM, Thomas Stewart wrote:

> Try
>
> expression(paste(integral(),"f(",tau,") d",tau,sep="")))
>
> it works for me.

It does "work" (albeit without properly including the requested limits  
of integrations), but if it is used as a teaching example, it will  
obscure the syntax of plotmath expressions. A simple version that gets  
the same result is:

  expression(integral()*f(tau)*d*tau))

Plotmath expressions are parsed from unquoted text with proper non- 
printing separators being "~" for space and "*" for juxtaposition. The  
plotmath paste() is not really the same as the base function paste(),  
despite identical names and its main value is as a method for allowing  
commas to also be used as separators. Frankly I'm a bit surprised you  
got away with adding the undocumented sep="" argument. My reading of  
the help page for plotmath would have lead me to predict that the text  
'sep=""' should appear in the output. Instead the "sep=" is ignored  
and the text string is appended to the end of the expression

Try for instance:

plot(1,1, main=expression(paste(a,b,c,d, sep="-") )  )

-- 
David.

>
> -tgs
>
> On Mon, Oct 4, 2010 at 9:25 AM, Czerminski, Ryszard <
> Ryszard.Czerminski at astrazeneca.com> wrote:
>
>> I would like to use greek "tau" as a symbol of variable to integrate
>> over in plotmath
>>
>> expression(integral(f(tau)*dtau, 0,t))
>>
>> but nothing seems to work. I tried d{\tau}, d\tau, etc.,
>> without any success
>>
>> Is it possible? How can I accomplish this?
>>
>> Best regards,
>> Ryszard
>>
>>
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David Winsemius, MD
West Hartford, CT