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Getting observations corresponding to each quartile

q <- quantile(faithful$eruptions)
> q
     0%     25%     50%     75%    100% 
1.60000 2.16275 4.00000 4.45425 5.10000 

I get the following result, the dataset is provided in R.

 head(faithful)
  eruptions waiting
1     3.600      79
2     1.800      54
3     3.333      74
4     2.283      62
5     4.533      85
6     2.883      55

I want a dataframe containing the data and an additional column for pointing out the quantile to which each observations belong. For example the final dataset should look like

     eruptions waiting Quartile
1     3.600      79      Q1
2     1.800      54      Q2
3     3.333      74
4     2.283      62
5     4.533      85
6     2.883      55

How can this be done?

like image 609
darkage Avatar asked Feb 25 '14 09:02

darkage


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1 Answers

Something along the lines of this? Use values from quantile function as values to cut the desired vector.

faithful$kva <- cut(faithful$eruptions, q)
levels(faithful$kva) <- c("Q1", "Q2", "Q3", "Q4")
faithful

    eruptions waiting  kva
1       3.600      79   Q2
2       1.800      54   Q1
3       3.333      74   Q2
4       2.283      62   Q2
5       4.533      85   Q4
like image 116
Roman Luštrik Avatar answered Oct 10 '22 04:10

Roman Luštrik