[R] Two == expressions in bquote

[Peter Dalgaard]

Larry Hotchkiss wrote:
> Hi,
> 
> I want to put text on a plot containing something like: a = b^2 = <squared numeric value of b> using bquote.
> 
> Example:
> 
>   mu = 5
>   plot(1:10,1:10)
>   text(2,8, bquote(delta == mu^2))            # This works
>   text(2.5,8, bquote(phantom(0) == .(mu^2)))  # but is unpredictable
> 
>   text(2,8, bquote(delta == mu^2 == .(mu^2))) # This doesn't work
> 
> The last text function returns the error:
> 
>      Error: unexpected '==' in "  text(2,8, bquote(delta == mu^2 =="

The comparison operators are not associative (they once were, but people 
were getting surprises from 3 > 2 > 1 evaluating to TRUE > 1 evaluating 
to FALSE). A set of suitably placed braces should clear things up:

text(2,8,bquote(delta == {mu^2 == .(mu^2)}))


> The first two text functions work in this example, using a default graphics window on a 64-bit Windows machine, and either R 2.11.0 development edition for 64-bit Windows or R 9.2.2 on the same machine ((x 86)). 
> 
> I don't mind the two statements except that when trying to automate this by using the base x coordinate + epsilon*max(x), for example --
> 
>   x <- 1:10
>   epsilon=0.05
>   text(2+esilon*max(x),8, bquote(phantom(0) == .(mu^2)))
> 
> for the x position on the 2nd text function, the position of the additional text is not predictable.
> 
> Thanks,
> 
> Larry Hotchkiss
> 
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-- 
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