[R] find most repeated item from column in dataframe

[Peter Alspach]

Tena koe Randy

If your dataframe is called randy, then the following seems to work:

aggregate(randy[,-(1:2)], list(randy[,1]), function(x) {tt <- table(x); names(tt)[which.max(tt)]})

HTH ....


Peter Alspach

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Randy Cass
> Sent: Wednesday, 25 August 2010 1:33 p.m.
> To: r-help at r-project.org
> Subject: [R] find most repeated item from column in dataframe
> 
> R users,
> 
> I am trying to find some way to find the value of a column that is
> repeated
> the most for each StandID of a dataframe.  I have research methods
> online
> and the help page, but have had no success in finding a solution.  I
> have
> tried using the table function but it returns items for the whole
> dataset
> and not by the StandID.  Any help will be appreciated.  Thanks in
> advance.
> 
> R version 2.11.1
> Windows 7
> Dataframe is imported from text file
> 
> StandID     PlotNum    HerbNum      Woody
> 001            1               1                    low
> 001            2               2                    medium
> 001            3               1                    low
> 001            4               3                    low
> 001            5               1                    high
> 001            6               2                    medium
> 002            1               1                    high
> 002            2               2                    high
> 002            3               2                    low
> 002            4               3                    high
> 002            5               1                    high
> 002            6               2                    medium
> 
> I would like to get the following from the dataframe
> 
> StandID    HerbNum      Woody
> 001          1                    low
> 002          2                    high
> 
> Thanks,
> 
> Randy
> 
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