[R] How to write a regression model for finding the radius of a cylinder given height and volume

[Rui Barradas]

Hello,

It really looked like homework. As for your question, maybe this helps.

URL <- "http://r.789695.n4.nabble.com/file/n4685033/cylinder.dat"
cyl <- read.table(URL, header = TRUE)
plot(vol ~ ht, data = cyl)

The vectors you want are simply

cyl$vol
cyl[["vol"]]
cyl[[1]]

and the same for height.
To find the radius you can note that your formula is equivalent to 
V=pi*r^2*H and use something like (note that the model has no intercept)

fit <- lm(vol ~ 0 + ht, data = cyl)
summary(fit)

r <- sqrt(coef(fit)/pi)
r

For linear models in R start by reading the file R-intro.pdf that comes 
with any installation of R, folder 'doc' chapter 11 Statistical models in R.

Hope this helps,

Rui Barradas

Em 11-02-2014 06:06, nivek escreveu:
> Thank you for your help. This is not homework however and my difficulty is in
> the fact that i cannot figure out how the declare a variable for the height
> or the volume given a data set where the matrix is already formed. I have
> looked on many sites for the is answer and it seems like it would be an easy
> one. So for this problem the provided data column 2 is the height data and
> column 1 is the volume. What command do I use to read those values and form
> a vector. Thank you for your time.
>
>
>
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