[R] plot formula 'x' is missing?

[Duncan Murdoch]

On 15/05/2010 1:22 AM, Giovanni Azua wrote:
> Hi Jorge and Dennis,
>
> Thank you for the hint! 
>
> However, I'm still very intrigued as to why it does not work using plot ... what is special about this specific formula that plot doesn't like it?
>
>   

There's nothing special about the formula.  plot() is simply saying (in 
a slightly unclear way) that it requires an argument named x, and you 
didn't pass one.  You would get past that error by leaving off the 
"formula =" part of your call, so that the first argument gets passed as 
x by default.  But then you'll get a new error:

 > 
plot(y~1/(1+exp(5.0993-0.1084*x)),data=data.frame(x=seq(0,100,length.out=1000)))
Error in eval(expr, envir, enclos) : object 'y' not found

The problem here is that you're asking to plot y versus an expression 
involving x, without defining what y is.  The version that works is the 
slightly odd looking

 > plot(1/(1+exp(5.0993-0.1084*x)) ~ 
x,data=data.frame(x=seq(0,100,length.out=1000)))

(or the version involving curve() that Jorge sent.)

Duncan Murdoch

> Best regards,
> Giovanni
>
> On May 15, 2010, at 7:12 AM, Jorge Ivan Velez wrote:
>   
>> Hi Giovanni,
>>
>> curve(1/(1+exp(5.0993-0.1084*x)), 0, 100)
>>
>> HTH,
>> Jorge
>>
>>
>> On Sat, May 15, 2010 at 12:43 AM, Giovanni Azua <> wrote:
>> Hello,
>>
>> I'd like to plot the logistic function for a specific model like this:
>>
>>     
>>> plot(formula=y~1/(1+exp(5.0993-0.1084*x)),data=data.frame(x=seq(0,100,length.out=1000)))
>>>       
>> Error in is.function(x) : 'x' is missing
>>
>> However, I get the 'x' is missing error above and don't know how to fix it ...
>>
>> Can anyone advice?
>> Thanks in advance,
>> Best regards,
>> Giovanni
>>
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>>
>>     
>
>
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