Re: [R] sd, mean with a frequency distribution matrix

2015-02-17 Thread JS Huang
Hi, Just learned another way to calculate sd for a frequency distribution matrix: > p <- matrix(c(10,3,20,4,30,5),ncol=2,byrow=TRUE) > p [,1] [,2] [1,] 103 [2,] 204 [3,] 305 > rep(p[,1],p[,2]) [1] 10 10 10 20 20 20 20 30 30 30 30 30 > sd(rep(p[,1],p[,2])) [1] 8.348471

Re: [R] sd, mean with a frequency distribution matrix

2015-02-16 Thread JS Huang
Hi, For the second one, sqrt((sum(p[,1]^2*p[,2])-(sum(p[,1]*p[,2]))^2/sum(p[,2]))/(sum(p[,2])-1)), please refer to the following link for an example to explain how it works. http://www.lboro.ac.uk/media/wwwlboroacuk/content/mlsc/downloads/var_stand_deviat_group.pdf For the first one: sd(unli

Re: [R] sd, mean with a frequency distribution matrix

2015-02-14 Thread dorian_pg
Thank you, I'll try as soon as possible! Il 13/Feb/2015 22:28 "JS Huang [via R]" < ml-node+s789695n470323...@n4.nabble.com> ha scritto: > Or if you want to perform the calculation without using sd: > > sqrt((sum(p[,1]^2*p[,2])-(sum(p[,1]*p[,2]))^2/sum(p[,2]))/(sum(p[,2])-1)) > > >

Re: [R] sd, mean with a frequency distribution matrix

2015-02-14 Thread JS Huang
Or if you want to perform the calculation without using sd: sqrt((sum(p[,1]^2*p[,2])-(sum(p[,1]*p[,2]))^2/sum(p[,2]))/(sum(p[,2])-1)) -- View this message in context: http://r.789695.n4.nabble.com/sd-mean-with-a-frequency-distribution-matrix-tp4703218p4703231.html Sent from the R help mailing

Re: [R] sd, mean with a frequency distribution matrix

2015-02-13 Thread JS Huang
Hi, Try this. > sd(unlist(sapply(1:dim(p)[1],function(i)rep(p[i,1],p[i,2] -- View this message in context: http://r.789695.n4.nabble.com/sd-mean-with-a-frequency-distribution-matrix-tp4703218p4703220.html Sent from the R help mailing list archive at Nabble.com. ___