[R] Working with duplicated rows

[Dimitris Rizopoulos]

try aggregate(), e.g.,

dat <- read.table(textConnection("long   lat   value

10     20      5

6      2       3

27    -3       9

10     20      10

4     -1       0

6      2       9"), header = TRUE)
closeAllConnections()


aggregate(dat["value"], list(Long = dat$long, Lat = dat$lat), sum)


I hope it helps.

Best,
Dimitris


Steve Murray wrote:
> Dear all,
> 
> 
> 
> I have a dataframe of 3 columns, consisting of 'longitude', 'latitude'
> and a corresponding 'value'. Where identical 'longitude' and 'latitude'
> pairs occur more than once, I want their corresponding 'value' to be
> summed and the 'pair' to only appear once.
> 
> 
> 
> For example:
> 
> 
> 
> long   lat   value
> 
> 10     20      5
> 
> 6      2       3
> 
> 27    -3       9
> 
> 10     20      10
> 
> 4     -1       0
> 
> 6      2       9
> 
> 
> 
> 
> 
> would be converted to something like:
> 
> 
> 
> long   lat   value
> 
> 
> 10     20      15
> 
> 
> 6      2       12
> 
> 
> 27    -3       9
> 
> 
> 4     -1       0
> 
> 
> 
> 
> 
> 
> ...as rows 1 and 4, 2 and 6 respectively are matched with respect to
> the 'long' and 'lat' columns. Their values in column 3 are then summed
> and reported as one row in the new dataframe.
> 
> 
> 
> How would I go about coding this in R?
> 
> 
> 
> Many thanks,
> 
> 
> 
> Steve
> 
> 
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-- 
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus Medical Center

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