[R] failure in simple calculation!!

[Mike Campana]

Hello

I have a dataframe, at least I think I created it by using:

DELTA <- as.data.frame(DELTA)

The dataframe has 2 columns made of numbers("data" and "delta")

If I use   DELTA$delta + 12
I get a sequence of NA  Warning message:
"+" not meaningful for factors in: Ops.factor(DELTA$deltatemp, 12)

What does this mean? Can you explain me please why I can not make this
simple calculation? And what can I do to the calculation?



further information:
mode(DELTA)
[1] "list"

DELTA$delta
.....
[685] 6.04  7.84  8.01  8.43  6.6   6.33  8.42  8.86  10.25 8.2   9.32  9.77
[697] 7.9   6.42  5.95
474 Levels: -0.02 -0.13 -0.22 -0.46 -0.55 -1.26 -1.83 -1.86 -2.45 -3.2 ...
9.9
What does this last row mean?

Thanks a lot for the answer and on general for the help contaned in the
mailing list

Mike