If your curve is in a 2-dim plane, then you can use the following

formula (in Tex notation):

\int_a^b \sqrt{1 + (\frac{df}{dx})^2} dx

So you need to take the derivative of your function first, and then

compute the integral of sqrt(1 + deriv^2) from a to b.

Here is a simple code to find the arclength of the curve: sin(x),

between -pi and pi.

##########################

arclen <- function(gexp, a, b) {

g <- function(x) { }

body(g) <- D(gexp, "x")

farc <- function(x) sqrt(1 + g(x)^2)

integrate(farc,low=a,upp=b)$val

}

gexp <- expression(sin(x))

arclen(gexp,-pi,pi)

###########################

Best,

Ravi.

----- Original Message -----

From: Greg Trafton <trafton@itd.nrl.navy.mil>

Date: Thursday, November 13, 2003 9:37 pm

Subject: [R] calculating arc length using R?

Hi, All. I have a function I want to know the plotted length of.

is it

possible to calculate the length of the function (e.g., arc length)?

for example, if I want to know the length of the line of

sin(x) from -pi to pi, how can I do that in R?

thanks!

greg

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is it

possible to calculate the length of the function (e.g., arc length)?

for example, if I want to know the length of the line of

sin(x) from -pi to pi, how can I do that in R?

thanks!

greg

______________________________________________

R-help at stat.math.ethz.ch mailing list

https://www.stat.math.ethz.ch/mailman/listinfo/r-help