On Dec 20, 2009, at 1:35 PM, Amit wrote:
Dear All,
I am trying to plot polynomial regression line to a scatterplot. I did
following so far:
x=c(1:9335)
y=read.table("gp.txt",header=T,sep="\t")
length(y$PCC) # y$PCC has values between 1 to 0 in decreasing order
[1] 9335
plot(x,y$PCC,col="red") #scatterplot between x and y$PCC
reg=lm(y$PCC~poly(x,6)) # calculating polynomial fit with degree 6
abline(reg,col="blue")
Warning message:
In abline(reg, col = "blue") :
only using the first two of 7regression coefficients
After the above warning a line is drawn in the graph parallel to the
y-axis. But I was expecting a curve line through the scatterplot.
Am I doing something wrong? Please help!
abline is designed to draw lines of the form y=a+bx, ... hence the
name. (And as documented on its help page for regression objects).
An effective method would be with lines and predict:
plot(cars, main="Stopping Distance versus Speed")
lines(cars$speed, predict(lm(dist~poly(speed, 6) ,data=cars) ),
col="red")
Best
Amit
_______________
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
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