Yes, I just tried the length() function and it worked beautifully.
Thank you. On 4/5/2012 6:01 PM, William Dunlap wrote:
I think you are looking for the function called length(). I cannot recreate your output, since I don't know what is in NZ_Conifers, but with the built-in dataset mtcars I get: > ddply(mtcars, .(cyl,gear,carb), summarize, MeanWt=mean(wt), N=length(wt)) cyl gear carb MeanWt N 1 4 3 1 2.46500 1 2 4 4 1 2.07250 4 3 4 4 2 2.68375 4 4 4 5 2 1.82650 2 5 6 3 1 3.33750 2 6 6 4 4 3.09375 4 7 6 5 6 2.77000 1 8 8 3 2 3.56000 4 9 8 3 3 3.86000 3 10 8 3 4 4.68580 5 11 8 5 4 3.17000 1 12 8 5 8 3.57000 1 > with(mtcars, sum(cyl==8& gear==3& carb==4)) # output line 10 [1] 5 If all you want is the count of things in various categories, you can use table instead of ddply and length: > with(mtcars, table(cyl, gear, carb)) , , carb = 1 gear cyl 3 4 5 4 1 4 0 6 2 0 0 8 0 0 0 , , carb = 2 gear cyl 3 4 5 4 0 4 2 6 0 0 0 8 4 0 0 ... Using ftable on table's output gives a nicer looking printout, but table's output is easier to use in a program. Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com-----Original Message----- From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On Behalf Of Christopher R. Dolanc Sent: Thursday, April 05, 2012 12:16 PM To: r-help@r-project.org Subject: [R] count() function I keep expecting R to have something analogous to the =count function in Excel, but I can't find anything. I simply want to count the data for a given category. I've been using the ddply() function in the plyr package to summarize means and st dev of my data, with this code: ddply(NZ_Conifers,.(ElevCat, DataSource, SizeClass), summarise, avgDensity=mean(Density), sdDensity=sd(Density), n=sum(Density)) and that gives me results that look like this: ElevCat DataSource SizeClass avgDensity sdDensity n 1 Elev1 FIA Class1 38.67768 46.6673478 734.87598 2 Elev1 FIA Class2 27.34096 23.3232470 820.22879 3 Elev1 FIA Class3 15.38758 0.7088432 76.93790 4 Elev1 VTM Class1 66.37897 70.2050817 24958.49284 5 Elev1 VTM Class2 39.40786 34.9343269 11782.95152 6 Elev1 VTM Class3 21.17839 12.3487600 1461.30895 But, instead of "sum(Density)", I'd really like counts of "Density", so that I know the sample size of each group. Any suggestions? -- Christopher R. Dolanc Post-doctoral Researcher University of California, Davis ______________________________________________ R-help@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.
-- Christopher R. Dolanc Post-doctoral Researcher University of California, Davis ______________________________________________ R-help@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.
