[R] optimize

[Joshua Wiley]

Hi Muhammad,

On Mon, Jan 3, 2011 at 6:52 AM, Muhammad Rahiz
<muhammad.rahiz at ouce.ox.ac.uk> wrote:
> Hi all,
>
> I'm trying to get the value of y when x=203 by using the intersect of three
> curves. The horizontal curve does not meet with the other two. How can I
> rectify the code below?

What is your code supposed to do?  This is one way to get three
intersecting curves, but I am not sure it is doing what you were
hoping to do with the sample code you sent.

ts <- seq(200, 209, 1)
dd <- c(NA,NA,NA,NA,1.87,1.83,1.86,NA,1.95,1.96)
xy <- lm(dd ~ ts)

plot(x = ts, y = dd, ylim = c(1.5,2))
abline(xy, col = "blue", lty = 2)
abline(v = 203, h = predict(xy, data.frame(ts = 203)),
  col = "blue", lty = 2)

Best regards,

Josh

>
> Thanks
>
> Muhammad
>
>  ts <- 1:10
>  dd <- 10:1
>
>  ts <- seq(200,209,1)
>  dd <- c(NA,NA,NA,NA,1.87,1.83,1.86,NA,1.95,1.96)
>
>  plot(ts,dd,ylim=c(1.5,2))
>  abline(lm(dd~ts),col="blue",lty=2)
>  abline(v=203,col="blue",lty=2)
>
>  xy <- lm(dd~ts)
>  fc <- function(x) coef(xy)[1] + x*coef(xy)[2]
>  val <- optimize(f=function(x) abs(fc(x)-203),c(1.5,2))
>  abline(h=val,col="blue",lty=2)
>
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>



-- 
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/