[R] How to get the equation of a graph after i have plotted the datas?
Marc Schwartz
marc_schwartz at comcast.net
Wed Feb 21 20:31:56 CET 2007
On Wed, 2007-02-21 at 18:20 +0000, ainhoaº lezama wrote:
>
> Hello!
>
> I have a doubt and i need a quick answer please!!
> I need to know if its possible to get in R the mathematical equation of a
> graph that you have plotted. I mean i know the y and x values, but i want
> the equation that relate them and that allow me to get the graph.
> This option is possible in Excel, but i have too many datas and i cant
> plotted them on it.
> If its possible in R, how?
>
>
> Thanks!!
Presuming that you are referring to a simple linear regression, using
some example data:
# Create some random data
# set the random seed first
set.seed(1)
x <- rnorm(15)
y <- x + rnorm(15)
# Create a linear model
LM <- lm(y ~ x)
# Plot the data
plot(x, y)
# Draw the fitted line, passing the model
# object as an argument
abline(LM)
# Now get the coefficients for the model
> coef(LM)
(Intercept) x
0.05510098 1.08897520
See ?abline, ?lm, ?coef and ?summary.lm for more information.
You would find value in reading "An Introduction to R", which is
available with your R installation or from the R web site under
"Manuals" as the above is covered there. Also the Posting Guide, for
which there is a link at the bottom of all e-mails coming from the R
lists.
If you need something a bit more, such as general curve fitting, using
RSiteSearch("curve fitting")
will get you many hits in the list archives and pointers to a variety of
functions.
HTH,
Marc Schwartz
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