help with aggregate()
On 2011-02-14 15:42, Sam Steingold wrote:
Hi,
I am trying to aggregate some data and I am confused by the results.
I load a data frame "all" from a csv file, and then I do:
(FOO,BAR,X,Y come from the header line in the csv file,
BTW, how do I rename a column?)
byFOO<- aggregate(list(all$BAR,all$QUUX,all$X/all$Y),
by = list(FOO=all$FOO),
FUN = mean);
I expect a data frame with 4 columns: FOO,BAR,QUUX and X/Y with all FOO
being different (they are character strings, do I need a special
incantation to turn them into factors?)
what I get is indeed a data frame but with names
[1] "FOO"
[2] "c.1.78e.11..4.38e.09..1.461e.11..4.3186e.10..1.1181e.10..5.5389e.10.."
[3] "c.33879300..3713870..190963000..7042170..4590010..91569200..12108200.."
[4] "c.1.37087599544937..1.72690992018244..1.82034830430797..1.70338983050847.."
I think that all you need is to provide names in your aggregate() call: byFOO <- aggregate(list(V1 = all$BAR, V2 = ....) For renaming variables in the dataframe any time, see help(names). Peter Ehlers
why? how do I fix the column names?
then I am trying to add to that same frame byFOO some other columns:
byFOO$Count<- aggregate(all$FOO, by = list(all$FOO), FUN = length);
byFOO$Mean<- aggregate(all$Value, by = list(all$FOO), FUN = mean);
byFOO$Total<- aggregate(all$Value, by = list(all$FOO), FUN = sum);
however, byFOO$Count et al are not columns in byFOO with the appropriate
names ("Count"&c) but data frames with columns "Group.1" and "x".
Luckily, at least it appears that byFOO$Count$Group.1 is the same as
byFOO$FOO, as they should be, although I don't see any function which
would check that two vectors are the same ("==" returns a vector which I
have to manually inspect for presence of "FALSE").
So, how do I aggregate the data frame?
How do I rename a column?
How do I check that two vectors are the same?
thanks a lot!
PS. I have not used R for a few years, so please be gentle...
PPS. Please do not tell me to RTFM - I did. At least tell me what to
search for.