On 4/19/2010 3:15 PM, Duncan Elkins wrote:
Hi, list-
I've got a large list of multi-column data and I'd like to filter
it according to a threshold, such as, "show me the values that are
above 0.4 for each line."
For instance, if the line of data were:
line
v1 v2 v3 v4 v5 v6 v7 v8 v9
1 -0.32 0.66 -0.35 -0.82 0.38 0.66 -0.02 -0.11 -0.64
I am assuming line is a data.frame.
> line <- data.frame(v1=-0.32, v2=0.66, v3=-0.35, v4=-0.82, v5=0.38,
v6=0.66, v7=-0.02, v8=-0.11, v9=-0.64)
> line
v1 v2 v3 v4 v5 v6 v7 v8 v9
1 -0.32 0.66 -0.35 -0.82 0.38 0.66 -0.02 -0.11 -0.64
I can do this
line[,line>= 0.4]
v2 v6
1 0.66 0.66
and
names(line[,line>= 0.4])
[1] "v2" "v6"
That's great. But, if there's only one value which passes the test, as in:
line[,line<= -0.7]
[1] -0.82
> line[,line <= -0.7, drop=FALSE]
v4
1 -0.82
> str(line[,line <= -0.7])
num -0.82
> str(line[,line <= -0.7, drop=FALSE])
'data.frame': 1 obs. of 1 variable:
$ v4: num -0.82
The single value loses its name attribute (in this case, I want "v4").
I guess I could kludge this by adding a dummy column that always
passes and trimming it out of the output, later, but it seems like
there ought to be an easier way. Am I misusing the bracket notation,
or ignorant of some obvious way to subset just one column and retain
its name?
Thanks,
Duncan
--
Brian Diggs
Senior Research Associate, Department of Surgery, Oregon Health &
Science University
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