[datatable-help] .I does not respect by

[Arunkumar Srinivasan]

Gabor,

It's the same as in 1.8.10 and 1.9.2. What is contradicting in ?data.table? It says under .I: ".I is an integer vector length .N holding the row locations in x for this group."

The row locations in x for b=1,2,1,2 are 1,2,3,4 which then becomes 1,3 and 2,4 for this group => b=1 and b=2 respectively.


Arun

From: Gabor Grothendieck ggrothendieck at gmail.com
Reply: Gabor Grothendieck ggrothendieck at gmail.com
Date: April 1, 2014 at 1:09:23 PM
To: datatable-help at lists.r-forge.r-project.org datatable-help at lists.r-forge.r-project.org
Subject:  [datatable-help] .I does not respect by  

In the following .I seems not to be within group.  

> dt <- data.table(a = 1:4, b = 1:2)  
> dt[, .I, by = b]  
b .I  
1: 1 1  
2: 1 3  
3: 2 2  
4: 2 4  
> packageVersion("data.table")  
[1] '1.9.3'  

This seems contrary to ?data.table.  


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