Try this:
with(foo, ave(Value, Label, FUN = seq)) will generate the time variable
xtabs(Value ~ ave(Value, Label, FUN = seq) + Label, foo)
On Wed, Oct 6, 2010 at 11:07 AM, Andre Easom <aea...@sportingindex.com>wrote:
> 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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