Hi Andras, This may be too simplistic, but how about
with(Interpolated, x[y==2][1]) ? On Tue, Feb 26, 2013 at 4:21 PM, Andras Farkas <motyoc...@yahoo.com> wrote: > Dear List, > > I have the following code: > > x <-c(0, 13.8333333333333, 38.1666666666667, 62.1666666666667, > 85.9166666666667, 108.916666666667) > y <-c(1.77, 2.39, 3, 2.65, 2.62, 1.8) > Interpolated <- approx(x, y,xout=0:tail(x, n=1),method="linear") > plot(Interpolated) > > in this code x is time in hours (cumulative), and y is a biological variable. > I am using linear interpolation assuming getting from y(i) to y(i+1) is a > linear path. I would like to calculate the time in this case that it takes to > surpass the y value of 2 for the first time. If you look at the plot, you > will see that the y value of 2 is crossed on 2 occasions: between the first > and second value of y (ie:1.77 to 2.39) and the fifth and sixth value of y > (ie2.62 and 1.8). In my case I really only care about the first "section" > (ie: how long it takes to get from 1.77 to 2.0). Any thoughts on how I could > calculate that chunk of the time would be greatly appreciated. > > let me present it in a simpler idea wher I can actually tell you what the > answer should be without having the code: > > x <-c(0, 12, 24, 36, 48, 60) > y <-c(1.5, 2, 3, 2.65, 2.62, 1.8) > Interpolated <- approx(x, y,xout=0:tail(x, n=1),method="linear") > plot(Interpolated) > > the answer in this case is 12 hours, which is the time spent in getting from > 1.5 to 2... > > hope I explained clearly what I am trying to do > > appreciate the help, > > Andras > > [[alternative HTML version deleted]] > > > ______________________________________________ > R-help@r-project.org mailing list > 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. > ______________________________________________ R-help@r-project.org mailing list 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.
