On Oct 3, 2010, at 10:22 PM, Gundala Viswanath wrote:
I have a data frame that looks like this:
print(df)
V2 V3 V4 V5 V6 V7 V8 V9 V10
V11 V12
1 FN 8.637 28.890 31.430 31.052 29.878 33.215 32.728 32.187 29.305
31.462
2 FP 19.936 30.284 33.001 35.100 30.238 34.452 35.849 34.185 31.242
35.635
3 TN 0.000 17.190 16.460 21.100 17.960 15.120 17.200 17.190 15.270
15.310
4 TP 22.831 31.246 33.600 35.439 32.073 33.947 35.050 34.472 31.228
33.701
How can I extract rows as specified, e.g.
I tried this to extract the first line ("FN") starting from V3 to V12:
fn <- df[1,df$V3:df$V12]
But it gives columns starting not from V3.
The ":" operator only works for numeric values in [,] or []. And even
then you would have been passing a very strange arguemtn to ":", since
df$V3 is a vector rather than a scalar. But these would also fail:
df[1, V3:V12]
df[1, "V3":"V12"]
These all work:
df[which(df$V2=="FN"), grep("^V3$", names(df)):grep("^V12$",
names(df)) ]
df[1, 2:11]
df[1, -1]
# the subset function may have tricked you into believing that my
statement about the ":" operator was false, but that function first
parses the select= (and subset=) expressions against column names and
returns column numbers before passing to ":"
subset(df, V2=="FN", select=-V2)
subset(df, V2=="FN", select=V3:V12)
What's the right way to do it?
- G.V.
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