median between matrix column

Dear Arun and Jessica,
thnx for your reply. it realy worked out.
regards
eliza

Date: Mon, 15 Oct 2012 05:55:55 -0700
From: smartpink111 at yahoo.com
Subject: Re: [R] median between matrix column
To: eliza_botto at hotmail.com
CC: r-help at r-project.org

HI,
May be this helps you (if I understand it correctly):
set.seed(1)
mat1<-matrix(sample(1:500,160,replace=TRUE),ncol=16)
res<-do.call(rbind,lapply(1:ncol(mat1[,-16]),function(i) median(sort(stack(as.data.frame(mat1[,c(i,16)]))[,1]))))
res
#       [,1]
#[1,] 239.0
#[2,] 238.0
#[3,] 181.5
#[4,] 244.5
#[5,] 265.0
#[6,] 212.0
#[7,] 228.5
#[8,] 233.0
#[9,] 182.5
#[10,] 239.5
#[11,] 233.5
#[12,] 220.0
#[13,] 235.0
#[14,] 259.0
#[15,] 227.0

A.K.





----- Original Message -----
From: eliza botto <eliza_botto at hotmail.com>
To: "r-help at r-project.org" <r-help at r-project.org>
Cc: 
Sent: Monday, October 15, 2012 8:20 AM
Subject: [R] median between matrix column


Dear useRs,

1.    how to calculate single median value for two columns of a matrix?
2.    i have a matrix of 16 columns and 365 rows, how to calculate median between columns 1 and 16, 2 and 16, 3 and 16, 4 and 16, 5 and 16 till 15th column. is there a loop command to do the said operation?

regards
eliza                          
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