Extrapolate x values from a defined y sequence
Hi Lionel, Your choice of variable names is a bit odd (the roles of x and y seem to be reversed from the usual.) Assuming that you are looking for linear interpolation (in spite of the subject of your email), does the following give you what you need? u1 <- approx(x=y1,y=x1,xout=y) u2 <- approx(x=y2,y=x2,xout=y) v <- u1$y + u2$y # At this point v is the sequence x1+x2 and y is as you specified it. # v # [1] 2.00000 6.00000 11.00000 16.29167 17.75000 18.41667 18.94444 19.47222 20.00000 # y # [1] 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 HTH, Eric On Mon, Jan 14, 2019 at 2:16 PM lionel sicot via R-help <
r-help at r-project.org> wrote:
Hello,
I have two sets of measurement :with the same x sequence
:x1<-1:10y1<-c(5,4.6,4.4,4.2,4,3.8,3.7,3.6,3,1)
x2<-1:10y2<-c(5,4.8,4.6,4.4,4.1,4,3.8,3.6,2.8,1)
I would like to sum these two curves in terms of x for a given sequence of
y (for example : y<-c(5,4.5,4,3.5,3,2.5,2,1.5,1)), that is to determine for
each y, an x1' from x1 and an x2' from x2 corresponding to y so that I can
plot y as a function of (x1'+x2').
I hope it is clear enough.
I think I can do it with a loop an some non-conventional R script (I'm not
a computer scientist) but i'm pretty sure that there is an elegant way to
do it with R.
It will be very kind if someone can give me some R functions to do
it.Thanks in advance,Ptit Bleu.
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