Hi,
I want to use reshape to convert from a skinny to a wide data format. My data
doesn't have a time variable attached - I have a series of ordered observations
for each subject, and it is this ordering that I am interested in (my objective
is to model the most recent observation based on the preceding observations).
From my understanding, prior to using reshape I have to attach a time variable,
which I have done using the code below. The problem is that it is extremely
slow - it took about 2 hours, on a dataset of about 800,000 lines. So my
questions are
1) Is there a (quick) way to use reshape without adding a time variable?
2) If the time variable is necessary, is there a quicker way to generate
it? (I know there is, because I did it in Excel...)
Thanks in advance for any advice.
Andre
> foo
Label Value
1 Alpha 0.57911322
2 Alpha 0.02270605
3 Alpha 0.58487636
4 Alpha 0.33741690
5 Alpha 0.38313390
6 Alpha 0.17298453
7 Beta 0.72645922
8 Beta 0.69010992
9 Beta 0.34449334
10 Gamma 0.13298949
11 Gamma 0.51267369
12 Gamma 0.03582759
13 Gamma 0.50352449
14 Delta 0.07146389
15 Delta 0.96315046
> foo[1,3] <- 1
> for (i in 2:length(foo[,1])) {
+ if (foo[i,1] ==foo[(i-1),1]) foo[i,3] <- foo[i-1,3] + 1
+ else foo[i,3] <- 1
+ }
> foo
Label Value V3
1 Alpha 0.57911322 1
2 Alpha 0.02270605 2
3 Alpha 0.58487636 3
4 Alpha 0.33741690 4
5 Alpha 0.38313390 5
6 Alpha 0.17298453 6
7 Beta 0.72645922 1
8 Beta 0.69010992 2
9 Beta 0.34449334 3
10 Gamma 0.13298949 1
11 Gamma 0.51267369 2
12 Gamma 0.03582759 3
13 Gamma 0.50352449 4
14 Delta 0.07146389 1
15 Delta 0.96315046 2
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