Thanks all. it works.
Just one more thing: if you look to this out put, > by(data1[,2:3], data1[,4], cor)[1] $`1` X Y X 1.0000000 0.4400451 Y 0.4400451 1.0000000 Q. How I can just pick the value of the correlation 0.4400451 from this output and call it sat corxy. Once again thank you all so much for your helps. Abou ========================== AbouEl-Makarim Aboueissa, Ph.D. Assistant Professor of Statistics Department of Mathematics & Statistics University of Southern Maine 96 Falmouth Street P.O. Box 9300 Portland, ME 04104-9300 Tel: (207) 228-8389 Email: [EMAIL PROTECTED] [EMAIL PROTECTED] Office: 301C Payson Smith >>> "Henrique Dallazuanna" <[EMAIL PROTECTED]> 8/16/2007 2:05 PM >>> For the 2nd item, perhaps: by(df[,1:2], df$index, FUN=cor) where df is your data.frame. -- Henrique Dallazuanna Curitiba-Paraná-Brasil 25° 25' 40" S 49° 16' 22" O On 16/08/07, AbouEl-Makarim Aboueissa <[EMAIL PROTECTED]> wrote: > > Dear All: > > Urgent help is needed. > > > I have a data set in matrix format of three columns: X, Y and index of > four groups (1,2,3,4). What I need to do is the following; > > 1- How I can subtract the sample mean of each group indexed 1,2,3,4 from > the > corresponding data values of this group and create new columns say > X-sample mean > and Y-sample mean? I tried to use the "tapply" but I have some > difficulties to restore the new data > > > 2- How I can use the "tapply" if possible or any other R-function to find > the correlation > coefficient between the X and Y columns for each group indexed > 1,2,3,4.? Could not use the "tapply". > > > I attached part of the data as txt file. > > > Thank you so much for your attention to this matter, and I look forward to > hear from you soon. > > Regards, > > Abou > > > Data: > ==== > x y index > 15807.24 12.5 4 > 15752.51 33.5 4 > 12893.76 01.5 3 > 8426.88 22.2 3 > 5706.24 333 3 > 3982.08 560 2 > 3642.62 670 2 > 295.68 124 1 > 215.40 104 1 > 195.40 204 1 > 4240.21 22.4 2 > 1222.72 45.9 2 > 1142.26 23.6 2 > 63.00 90.1 1 > 1216.00 82.4 2 > 2769.60 111 2 > 1790.46 34.7 2 > 26.10 26.10 1 > 19676.83 0.99 4 > 10920.60 203 3 > 6144.00 46 3 > 4534.48 4534.48 3 > 40000.00 65 4 > 29500.00 56 4 > 17100.00 77 4 > 9000.00 435 3 > 6300.00 84 3 > 3962.88 334 2 > 5690.00 653 3 > 3736.00 233 2 > 2750.00 22 2 > 1316.00 345 2 > 4595.00 4595.00 3 > 5928.00 45 3 > 2645.70 0.00 2 > 2580.24 454 2 > 6547.34 6547.34 3 > 1615.68 5 2 > 194.06 55 1 > 184.80 6 1 > 82.94 44 1 > 16649.00 56 4 > 4500.00 74 3 > 1600.00 744 2 > > ================= > > > > ========================== > AbouEl-Makarim Aboueissa, Ph.D. > Assistant Professor of Statistics > Department of Mathematics & Statistics > University of Southern Maine > 96 Falmouth Street > P.O. Box 9300 > Portland, ME 04104-9300 > > Tel: (207) 228-8389 > Email: [EMAIL PROTECTED] > [EMAIL PROTECTED] > Office: 301C Payson Smith > > > ______________________________________________ > R-help@stat.math.ethz.ch 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. > > > ______________________________________________ R-help@stat.math.ethz.ch 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.