[R] y needing more than 2 functions
Petr Savicky
savicky at cs.cas.cz
Tue Mar 27 09:07:10 CEST 2012
On Mon, Mar 26, 2012 at 07:48:07PM -0400, Aimee Jones wrote:
> Dear all,
>
> I'm aware if y has two separate functions (depending on the conditions
> of x) you can use the ifelse function to separate y into two separate
> functions depending on input. How do you do this if there a multiple
> different conditions for x?
>
> for example,
>
> y fits the following between t>0 & t<15----->function(t) t^2, y fits
> the following between t>15 & t<30-----> function(t) t^3, y fits the
> following between t>30 &t<45--->function(t) t^4 etc
Hi.
Try the following.
bounds <- c(0, 15, 30, 45)
x <- seq(4, 44, length=51)
valfunc <- cbind(x^2, x^3, x^4)
indfunc <- findInterval(x, bounds)
y <- valfunc[cbind(1:nrow(valfunc), indfunc)]
# verify
range(x[y == x^2]) # [1] 4.0 14.4
range(x[y == x^3]) # [1] 15.2 29.6
range(x[y == x^4]) # [1] 30.4 44.0
Hope this helps.
Petr Savicky.
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