First of all - thanks to the R-users who replied my previous mail "Selecting Best Regression Equation". However, seems i've got some other problems now -
My data in c:\leafbrn.txt file is- -------------------------------------- i x1 x2 x3 y 1 3.05 1.45 5.67 0.34 2 4.22 1.35 4.86 0.11 3 3.34 0.26 4.19 0.38 4 3.77 0.23 4.42 0.68 5 3.52 1.10 3.17 0.18 6 3.54 0.76 2.76 0.00 7 3.74 1.59 3.81 0.08 8 3.78 0.39 3.23 0.11 9 2.92 0.39 5.44 1.53 10 3.10 0.64 6.16 0.77 11 2.86 0.82 5.48 1.17 12 2.78 0.64 4.62 1.01 13 2.22 0.85 4.49 0.89 14 2.67 0.90 5.59 1.40 15 3.12 0.92 5.86 1.05 16 3.03 0.97 6.60 1.15 17 2.45 0.18 4.51 1.49 18 4.12 0.62 5.31 0.51 19 4.61 0.51 5.16 0.18 20 3.94 0.45 4.45 0.34 21 4.12 1.79 6.17 0.36 22 2.93 0.25 3.38 0.89 23 2.66 0.31 3.51 0.91 24 3.17 0.20 3.08 0.92 25 2.79 0.24 3.98 1.35 26 2.61 0.20 3.64 1.33 27 3.74 2.27 6.50 0.23 28 3.13 1.48 4.28 0.26 29 3.49 0.25 4.71 0.73 30 2.94 2.22 4.58 0.23 --------------------------------------
And my applied R codes are-
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> options(prompt=" R > " )
R > leafbrn1<-read.table("c:\\leafbrn.txt",header=T)
R > leafbrn.data1<-data.frame(leafbrn1)
R > attach(leafbrn.data1)
R > x1sq<-x1^2;x2sq<-x2^2;x3sq<-x3^2;x1x2<-x1*x2;x1x3<-x1*x3;x2x3<-x2*x3;
R > leafbrn <- cbind(leafbrn1,x1sq,x2sq,x3sq,x1x2,x1x3,x2x3)
R > detach(leafbrn.data1)
R > leafbrn.data<-data.frame(leafbrn)
R > attach(leafbrn.data)
R > X<-cbind(x1,x2,x3,x1sq,x2sq,x3sq,x1x2,x1x3,x2x3)
R > Y<-y
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But using package leaps {leaps downloaded from http://cran.r-project.org/bin/windows/contrib/1.7/leaps_2.6.zip} with the following command -
R > leaps(X,Y,int=TRUE, method=c("Cp"), names=NULL, df=NROW(x), nbest=choose(9,5), strictly.compatible=T)
# Since there are 9 terms and its combination is higher in 4 or 5
gives the message -
Error in leaps.exhaustive(a) : Exhaustive search will be S L O W, must specify really.big=T
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1. What to do ? I don't understand where to set really.big=T.
2. Why do we need strictly.compatible=T ?
3. Can we simultaneously use Cp, r2, adjr2 in method?
4. I still have problem with FORWARD / BACKWARD / STEPWISE methods. Can anyone please help me to solve the above problem by using these methods (I use R 1.7.1)?
5. In S-plus 4, is the following command correct for the above problem? - it seem to give me too many calculations and i don't understand which one is the result!
> options(prompt=" S+ > " )
S+ > stepwise(X, Y,intercept=T, tolerance=1.e-07,method="exhaustive", size.max=ncol(X), nbest=choose(9,5), f.crit=4, plot=T, time=0.02)
Any response / help / comment / suggestion / idea / web-link / replies will be greatly appreciated.
Thanks in advance for your time.
_______________________
Mohammad Ehsanul Karim <[EMAIL PROTECTED]> Institute of Statistical Research and Training University of Dhaka, Dhaka- 1000, Bangladesh
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