Re: [R] get top n rows group by a column from a dataframe

[Phil Spector]

Richard -
   Is this what you're looking for?

sdata = data.frame(company=sample(LETTERS[1:8],1000,replace=TRUE),

                     person=1:1000,
                     salary=rnorm(1000))

splitsdata = split(sdata,sdata$company)
res = do.call(rbind,sapply(splitsdata,simplify=FALSE,

                       function(x)x[order(x$salary,decreasing=TRUE),][1:5,]))

row.names(res) = NULL
res

   company person   salary
1        A    560 2.721923
2        A    538 2.456439
3        A    594 2.093376
4        A    947 1.960166
5        A    334 1.544756
6        B    671 2.484698
7        B    533 2.328799
         . . .
                                        - Phil Spector
                                         Statistical Computing Facility
                                         Department of Statistics
                                         UC Berkeley
                                         spec...@stat.berkeley.edu



On Thu, 16 Sep 2010, Tan, Richard wrote:

Hi Richard



Thanks for the suggestion, but I want top 5 salary for each company, not
the whole list.  I don't see how your way can work?



Thanks,

Richard



From: RICHARD M. HEIBERGER [mailto:r...@temple.edu]
Sent: Thursday, September 16, 2010 11:53 AM
To: Tan, Richard
Cc: r-help@r-project.org
Subject: Re: [R] get top n rows group by a column from a dataframe

tmp <- data.frame(matrix(rnorm(30), 10, 3,

                          dimnames=list(letters[1:10],
                                        c("company", "person",
"salary"))))

tmp

     company     person      salary
a -1.04590176 -0.7841855  1.07150503
b -1.06643101  0.6545647  0.43920454
c  0.72894531 -1.3812867  0.41313659
d -0.39265263 -0.3871271  0.69404325
e  0.54028124  0.7124772  0.66630904
f -1.46931714 -0.3823353  0.03069797
g -0.33283666 -0.6351862  0.37920017
h -0.79977129  0.2605315  0.92373900
i  0.80614119  0.3727227 -1.16560563
j  0.03165012  0.4690400 -0.81966285

order(tmp$person, decreasing=TRUE)[1:min(5, length(tmp$person))]

[1]  5  2 10  9  8

tmp[order(tmp$person, decreasing=TRUE)[1:min(5, length(tmp$person))],]

     company    person     salary
e  0.54028124 0.7124772  0.6663090
b -1.06643101 0.6545647  0.4392045
j  0.03165012 0.4690400 -0.8196628
i  0.80614119 0.3727227 -1.1656056
h -0.79977129 0.2605315  0.9237390

You can easily write a function for that.
top <- function(DF, varname, howmany) {}


On Thu, Sep 16, 2010 at 11:39 AM, Tan, Richard <r...@panagora.com>
wrote:

        Hi, is there an R function like sql's TOP key word?

        I have a dataframe that has 3 columns: company, person, salary

        How do I get top 5 highest paid person for each company, and if
I have
        fewer than 5 people for a company, just return all of them?

        Thanks,

        Richard


        [[alternative HTML version deleted]]

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