# Re: [R] help with sapply, plot, lines

From: Berton Gunter <gunter.berton_at_gene.com>
Date: Wed 21 Dec 2005 - 06:53:58 EST

> Now, I want to plot the same function for different values of
> str, as follows:
>
> sapply(seq(0,0.3,0.05),function(s) {str<-s;
> lines(seq(0.01,0.99,0.01),sigma(seq(0.01,0.99,0.01)))})
>
> Hoping that sigma will lexically scope into str and that
> lines will appear on the same plot as the one I first drew above.
>

Lexical scoping means that the free variable str in sigma is looked for in the enclosing environment, not the parent environment. This is the environment in which sigma was defined, not called. Hence str is constant in your calls and you get identical results at each call. See the section 3.3.1 of the R FAQ. In your example, the straightforward solution is to pass str as an argument of sigma.

• Bert Gunter Genentech Non-Clinical Statistics South San Francisco, CA

"The business of the statistician is to catalyze the scientific learning process." - George E. P. Box

> -----Original Message-----
> From: r-help-bounces@stat.math.ethz.ch
> [mailto:r-help-bounces@stat.math.ethz.ch] On Behalf Of Uzuner, Tolga
> Sent: Tuesday, December 20, 2005 10:18 AM
> To: 'r-help@stat.math.ethz.ch'
> Subject: [R] help with sapply, plot, lines
>
> Hi,
>
> I am trying to plot multiple lines on a graph.
>
> The function is particularly simple:
>
> sigma<-function(lambda) atm-2*rr*(lambda-0.5)+16*str*(lambda-0.5)^2
>
> which uses the variables atm, rr and str...
>
> I define these as such:
>
> atm<-0.4
> rr<-0.2
> str<-0.1
>
>
> and this plots fine:
>
> plot(seq(0.01,0.99,0.01),sigma(seq(0.01,0.99,0.01)),ylim=c(0,1))
>
> Now, I want to plot the same function for different values of
> str, as follows:
>
> sapply(seq(0,0.3,0.05),function(s) {str<-s;
> lines(seq(0.01,0.99,0.01),sigma(seq(0.01,0.99,0.01)))})
>
> Hoping that sigma will lexically scope into str and that
> lines will appear on the same plot as the one I first drew above.
>
> Instead, I just get this:
> > sapply(seq(0,0.3,0.05),function(s) {str<-s;
> lines(seq(0.01,0.99,0.01),sigma(seq(0.01,0.99,0.01)))})
> [[1]]
> NULL
>
> [[2]]
> NULL
>
> [[3]]
> NULL
>
> [[4]]
> NULL
>
> [[5]]
> NULL
>
> [[6]]
> NULL
>
> [[7]]
> NULL
>
> and the plot does not change.
>
> Any assistance appreciated.
>
> Regards,
> Tolga
>
>
>
>
>
>
>
>
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