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Asked: 2026-06-10T12:39:00+00:00

Possible Duplicate: Idiomatic R code for partitioning a vector by an index and performing

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Possible Duplicate:
Idiomatic R code for partitioning a vector by an index and performing an operation on that partition
How to calculate median of profits for a particular country

I am trying to find average of a column by using another column in R.It’s so easy to do it in SQL but not able to find proper functions and implement them.Here is some sample data as below.

data("Forbes2000", package = "HSAUR")
head(Forbes2000)

##    rank                name        country             category  sales profits  assets marketvalue
## 1    1           Citigroup  United States              Banking  94.71   17.85 1264.03      255.30
## 2    2    General Electric  United States        Conglomerates 134.19   15.59  626.93      328.54
## 3    3 American Intl Group  United States            Insurance  76.66    6.46  647.66      194.87
## 4    4          ExxonMobil  United States Oil & gas operations 222.88   20.96  166.99      277.02
## 5    5                  BP United Kingdom Oil & gas operations 232.57   10.27  177.57      173.54
## 6    6     Bank of America  United States              Banking  49.01   10.81  736.45      117.55
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1 Answer

  1. Editorial Team

    With a data.frame named dat that looked like:

         rank              name  country       category  sales profits assets marketvalue
21     21   DaimlerChrysler Germany    Consumer_dur 157.13    5.12 195.58       47.43

    Try (untested d/t the numerous spaces in the text preventing read.table from making sense of it): 

    aggregate(dat[ , c("sales", "profits", "assets", "marketvalue")],   # cols to aggregate
          dat["country"],                                           # group column
          FUN=mean)                          # aggregation function
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