Dear Mr. Murdoch,

I now understand that curve does not know how to guess what x in curve(x)
means.  As you say, it might guess that x means a function, and if there is
a function x, execute it.  This is seen in the example:

> x <- function(x) { x }
> curve(x)

I think, if curve guesses I have a function x and there is no function x, it
might just plot y = x, but as you say, there would be other cases where
curve would still fail to guess correctly.

Thank you for support.
Abhilash B.



On Sun, Jun 5, 2011 at 3:39 PM, Duncan Murdoch <murdoch.duncan@gmail.com>wrote:

> On 11-06-05 1:07 PM, Abhilash Balakrishnan wrote:
>
>> Dear Sirs,
>>
>> I am a new user of the R package.  When I try to use the curve function it
>> confuses me.
>>
>>  curve(x^2)
>>>
>> Works fine.
>>
>>  curve(x)
>>>
>> Makes a complaint I don't understand.  Why is x^2 valid and x is not?
>>
>
> curve() is a convenience function, and it tries to guess what you mean.
>  Sometimes it gets it wrong.
>
> In the first case, it is clear you want to graph x^2.  In the second it
> guesses you have a function named x and want to graph that.  You don't, so
> it fails.
>
> Probably it could try again after the first failure, but I'd guess there
> will always be strange cases where it does weird things.
>
> Duncan Murdoch
>
>
>> I check the documentation of curve, and it says the first argument must be
>> an expression containing x.
>>
>>  expression(x)
>>>
>> Is an expression containing x.
>>
>>  curve(expression(x))
>>>
>> Makes a different complaint and mentions different lengths of x and y (but
>> I
>> use no y here).
>>
>> I understand that plotting the function y(x) = x is rather silly, but I
>> want
>> to know what I am doing wrong, for the sake of my understanding of how R
>> works.
>>
>> Thank you for support.
>> Abhilash B.
>>
>>        [[alternative HTML version deleted]]
>>
>> ______________________________________________
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>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
>

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