Hello! I have a dataset like this: X1 X2 X3 X4 X5 X6 X7 X8 1 2 2 1 2 3 2 6 2 3 2 5 7 9 1 3 1 9 12 6 1 1 3 6 The columns X1-X6 contains ordinary numeric values. X7 contains the number of the first column that the rowMeans should be calculated from and X8 contains the last column that should be included in the rowMeans. when I try test <- (df[,df$X7:df$X8]) the rowMeans are calculated based on the values in the X7 and X8 in the first row only. Thanks in advance! /Marine
Calculating rowMeans from different columns in each row?
3 messages · Marine Andersson, rex.dwyer at syngenta.com, Phil Spector
-----Original Message----- From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of Marine Andersson Sent: Thursday, February 10, 2011 3:53 PM To: r-help at r-project.org Subject: [R] Calculating rowMeans from different columns in each row? Hello! I have a dataset like this: X1 X2 X3 X4 X5 X6 X7 X8 1 2 2 1 2 3 2 6 2 3 2 5 7 9 1 3 1 9 12 6 1 1 3 6 The columns X1-X6 contains ordinary numeric values. X7 contains the number of the first column that the rowMeans should be calculated from and X8 contains the last column that should be included in the rowMeans. when I try test <- (df[,df$X7:df$X8]) the rowMeans are calculated based on the values in the X7 and X8 in the first row only. Thanks in advance! /Marine ______________________________________________ [Dwyer Rex USRE] Well, if you print df$X7:df$X8, you'll see why... you can't ":" together two vectors:
c(1,2,3):c(8,10,12)
[1] 1 2 3 4 5 6 7 8 Warning messages: 1: In c(1, 2, 3):c(8, 10, 12) : numerical expression has 3 elements: only the first used 2: In c(1, 2, 3):c(8, 10, 12) : numerical expression has 3 elements: only the first used
So try: apply(df,1, function(v) {n=length(v); mean(v[v[n-1]:v[n]]) })
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Marine -
Assuming your data frame is named "df", I think
apply(df,1,function(x)mean(x[x[7]:x[8]]))
will give you what you're looking for.
- Phil Spector
Statistical Computing Facility
Department of Statistics
UC Berkeley
spector at stat.berkeley.edu
On Thu, 10 Feb 2011, Marine Andersson wrote:
Hello! I have a dataset like this: X1 X2 X3 X4 X5 X6 X7 X8 1 2 2 1 2 3 2 6 2 3 2 5 7 9 1 3 1 9 12 6 1 1 3 6 The columns X1-X6 contains ordinary numeric values. X7 contains the number of the first column that the rowMeans should be calculated from and X8 contains the last column that should be included in the rowMeans. when I try test <- (df[,df$X7:df$X8]) the rowMeans are calculated based on the values in the X7 and X8 in the first row only. Thanks in advance! /Marine
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