# [R] regression methods for circular(?) data.

Witold Eryk Wolski W.E.Wolski at ncl.ac.uk
Mon Sep 26 18:20:32 CEST 2005

```Hi,

I do not know the intercept and slope.
And you have to know them in order to do something like:
ix<-(y < 0.9*(x-50)/200

I am right?

cheers

(Ted Harding) wrote:
> On 26-Sep-05 nwew wrote:
>
>>Dear R-users,
>>
>>I have the following data
>>
>>x <- runif(300,min=1,max=230)
>>
>>y <- x*0.005 + 0.2
>>y <- y+rnorm(100,mean=0,sd=0.1)
>>y <- y%%1 #  <------- modulo operation
>>plot(x,y)
>>
>>and would like to recapture the slope (0.005) and intercept(0.2).
>>I wonder if there are any clever algorithms to do this. I was
>>looking at the function lm.cirucalar. Is this the method to use?
>>If, which of the references is best too look at?
>>
>>Eryk
>
>
> Hi Eryk,
>
> If you know the modulus (in your case 1.0) and you get data that
> look like the result of your "plot(x,y)", then I wouldn't mess
>
> I would simply do something like
>
> y1<-y
> ix <- ix<-(y < 0.9*(x-50)/200)
> y1[ix] <- y1[ix]+1.0
> lm(y1~x)
>
> (the constants 0.9/200, -50 being chosen to give a good separation
> on the graph).
>
> On the other hand, if there are good reasons why this very simple
> approach is not suitable, then if we knew what they were a more
>
> Best wishes,
> Ted.
>
>
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> E-Mail: (Ted Harding) <Ted.Harding at nessie.mcc.ac.uk>
> Fax-to-email: +44 (0)870 094 0861
> Date: 26-Sep-05                                       Time: 15:56:48
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