R help - Jun 2012 - How to plot linear, cubic and quadratic fitting curve in a figure?

Hi R experts, 
Could you please help me to fit a linear, cubic and quadratic curve in a figure?
I was trying to show all these three fitting curves with different colour in one
figure.
I spent substantial time to figure it out, but I could not. 

I have given here a example and what I did for linear, but no idea for cubic and
quadratic fitting curve

> dput(test)
structure(list(sp = c(4L, 5L, 9L, 12L, 14L), env = c(12L, 18L, 
20L, 17L, 15L)), .Names = c("sp", "env"), class =
"data.frame", row.names = c(NA,
-5L))
> plot(test$sp~test$env, main = "S vs. temp", xlim=c(0,20),
ylim=c(0,14), ylab="S",xlab="env")
> linear<-lm(test$sp~test$env)
> quadratic<-lm(test$sp~test$env+I(test$env^2))
> #summary(quadratic)
> cubic<-lm(test$sp~test$env+I(test$env^2)+I(test$env^3))
> #summary(cubic)
> #fitting curve
> abline(linear)
> 
Here I did for linear, but now I don't how I can plot quadratic and cubic
line in the figure with different colour. I further wanted to put r2 value on
the top of the fitting line.
ON linear fitting curve, I can see the line originated from left to right (cover
whole x axis). I could not plot the line only within the data set.
Would any one help me to figure it? I think it is not difficult but for me- it
is really taking time.

Thanks and waiting for your suggestions

sincerely, 
Kristi Glover


 
 		 	   		  
	[[alternative HTML version deleted]]

Hi, Kristi-
Here is an option.
?curve...to add the polynomials to your graph
?text....for adding the R2 to you plot
Ken


On 06/13/12, Kristi Glover  wrote:
> 
> Hi R experts, 
> Could you please help me to fit a linear, cubic and quadratic curve in a
figure? I was trying to show all these three fitting curves with different
colour in one figure.
> I spent substantial time to figure it out, but I could not. 
> 
> I have given here a example and what I did for linear, but no idea for
cubic and quadratic fitting curve
> 
> 
> > dput(test)
> structure(list(sp = c(4L, 5L, 9L, 12L, 14L), env = c(12L, 18L, 
> 20L, 17L, 15L)), .Names = c("sp", "env"), class =
"data.frame", row.names = c(NA,
> -5L))
> > plot(test$sp~test$env, main = "S vs. temp", xlim=c(0,20),
ylim=c(0,14), ylab="S",xlab="env")
> > linear<-lm(test$sp~test$env)
> > quadratic<-lm(test$sp~test$env+I(test$env^2))
> > #summary(quadratic)
> > cubic<-lm(test$sp~test$env+I(test$env^2)+I(test$env^3))
> > #summary(cubic)
> > #fitting curve
> > abline(linear)
> > 
> Here I did for linear, but now I don't how I can plot quadratic and
cubic line in the figure with different colour. I further wanted to put r2 value
on the top of the fitting line.
> ON linear fitting curve, I can see the line originated from left to right
(cover whole x axis). I could not plot the line only within the data set.
> Would any one help me to figure it? I think it is not difficult but for me-
it is really taking time.
> 
> Thanks and waiting for your suggestions
> 
> sincerely, 
> Kristi Glover
> 
> 
> 
> 
> [[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

> dput(test)
structure(list(sp = c(4L, 5L, 9L, 12L, 14L), env = c(12L, 18L,
20L, 17L, 15L)), .Names = c("sp", "env"), class =
"data.frame", row.names =
c(NA,
-5L))
> plot(test$sp~test$env, main = "S vs. temp", xlim=c(0,20),
ylim=c(0,14),
> ylab="S",xlab="env")
> linear<-lm(test$sp~test$env)
> quadratic<-lm(test$sp~test$env+I(test$env^2))
> #summary(quadratic)
> cubic<-lm(test$sp~test$env+I(test$env^2)+I(test$env^3))
> #summary(cubic)
> #fitting curve
> abline(linear)
>
Thanks and waiting for your suggestions

sincerely,
Kristi Glover

Try adding the following lines of code
cq = coef(quadratic)
cc = coef(cubic)
newenv = seq(min(test$env), max(test$env), by = (max(test$env) - 
min(test$env))/500)
sp.quad = cq[1] + cq[2]*newenv +cq[3]*newenv^2
lines(newenv,sp.quad, col='red')

sp.cubic = cc[1] + cc[2]*newenv +cc[3]*newenv^2 +cc[4]*newenv^3
lines(newenv, sp.cubic, col='blue', lty=2)

------------------------------------------
Robert W. Baer, Ph.D.
Professor of Physiology
Kirksville College of Osteopathic Medicine
A. T. Still University of Health Sciences
800 W. Jefferson St.
Kirksville, MO 63501
660-626-2322
FAX 660-626-2965

On Jun 13, 2012, at 10:29 AM, Kristi Glover wrote:
>
> Hi R experts,
> Could you please help me to fit a linear, cubic and quadratic curve  
> in a figure? I was trying to show all these three fitting curves  
> with different colour in one figure.
> I spent substantial time to figure it out, but I could not.
>
> I have given here a example and what I did for linear, but no idea  
> for cubic and quadratic fitting curve
>
>
>> dput(test)
> structure(list(sp = c(4L, 5L, 9L, 12L, 14L), env = c(12L, 18L,
> 20L, 17L, 15L)), .Names = c("sp", "env"), class =
"data.frame",
> row.names = c(NA,
> -5L))
>> plot(test$sp~test$env, main = "S vs. temp", xlim=c(0,20),  
>> ylim=c(0,14), ylab="S",xlab="env")
>> linear<-lm(test$sp~test$env)
>> quadratic<-lm(test$sp~test$env+I(test$env^2))
>> #summary(quadratic)
>> cubic<-lm(test$sp~test$env+I(test$env^2)+I(test$env^3))
>> #summary(cubic)
>> #fitting curve
>> abline(linear)
>>
> Here I did for linear, but now I don't how I can plot quadratic and  
> cubic line in the figure with different colour. I further wanted to  
> put r2 value on the top of the fitting line.
> ON linear fitting curve, I can see the line originated from left to  
> right (cover whole x axis). I could not plot the line only within  
> the data set.
> Would any one help me to figure it? I think it is not difficult but  
> for me- it is really taking time.
>
There is the poly  function that does the heavy lifting and also  
preserves the statistical propriety of polynomial fits.


 > quadratic<-lm( sp ~ poly(env, 2), data=test)
 > #summary(quadratic)
 > cubic<-lm( sp ~ poly(env, 3), data=test)
 > #summary(cubic)
 > #fitting curve

 > plot( sp~ env, data=test, main = "S vs. temp", xlim=c(0,20),  
ylim=c(0,14), ylab="S",xlab="env")

 > abline(linear)
 > lines( test$env[order(test$env)] , predict(quadratic)[order(test 
$env)] )
 > lines( test$env[order(test$env)] , predict(cubic)[order(test 
$env)] , col="red")

You can substitute:

lines(  x=seq( min(test$env) , max(test$env), len=100) ,
  y= predict(model, data.frame(env=seq( min(test$env) , max(test$env),  
len=100) ) ) )

... if you want smoother output.

-- 
David Winsemius, MD
West Hartford, CT