Using column names where you used column numbers would work:
example <- data.frame(
check.names = FALSE,
Nuclei = c(133L, 96L, 62L, 60L),
`Positive Nuclei` = c(96L, 70L, 52L, 50L),
Slide = factor(c("A1", "A1", "A2", "A2"), levels = c("A1", "A2")))
aggregate(example["Nuclei"], by=example["Slide"], sum)
# Slide Nuclei
#1 A1 229
#2 A2 122
aggregate(example[1], by=example[3], sum)
# Slide Nuclei
#1 A1 229
#2 A2 122
Many people find that the functions in the dplyr or plyr packages
are worth the trouble to learn about.
Bill Dunlap
TIBCO Software
wdunlap tibco.com
On Fri, Jan 22, 2016 at 11:20 AM, Ed Siefker <ebs15...@gmail.com> wrote:
> 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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