[R] aggregate and the $ operator
Ed Siefker
ebs15242 at gmail.com
Fri Jan 22 20:20:59 CET 2016
Aggregate does the right thing with column names when passing it
numerical coordinates.
Given a dataframe like this:
Nuclei Positive Nuclei Slide
1 133 96 A1
2 96 70 A1
3 62 52 A2
4 60 50 A2
I can call 'aggregate' like this:
> aggregate(example[1], by=example[3], sum)
Slide Nuclei
1 A1 229
2 A2 122
But that means I have to keep track of which column is which number.
If I try it the
easy way, it doesn't keep track of column names and it forces me to
coerce the 'by'
to a list.
> aggregate(example$Nuclei, by=list(example$Slide), sum)
Group.1 x
1 A1 229
2 A2 122
Is there a better way to do this? Thanks
-Ed
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