[R] Remove part of string in colname and calculate mean for columns groups

[Dieter Menne]

Joel Fürstenberg-Hägg wrote:
> 
> 
> 
> I have two question. First, I wonder how to remove a part of the column
> names in a matrix? I would like to remove the "_ACCX" or "_NAX" part
> below. Is there a method where the "_" as well as all characters after i
> can be removed?
> 
> Secondly, I would like to calculate the mean of each column group in the
> matrix, for instance all columns beginning with "Akita", and save all new
> columns as a new matrix. 
>  
> 

If you do that in the example you gave, duplicate column names would be the
result, but let's assume that was a typo.

# Simplify names
data = data.frame(Akita.0_ACC1=1:2,Akita.1_ACC2=2:3,Alc.0_ACC1=3:4)
names(data) = sub("_.*","",names(data))
# Make a new data frame with the Akitas only
dataAkita = data[,grep("Akita",names(data))]

To do the averaging, check the examples in package plyr. 

Dieter






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