On Tue, 17 May 2005, Uwe Ligges wrote:
Anders Schwartz Corr wrote:Oops,
I just erased all my data using this gizmo that I thought would replace -9 with NA.
A) Can I get my tcn5 back?
As you got it the first time. There is nothing like "undo".
B) How do I do it right next time, I learned my lesson, I'll never do it again, I promise!
By vectorization:
tcn5[tcn5 == -9] <- NA
That will work if tcn5 contains NAs, but only because NA indices on the lhs are now ignored for matrices (if tcn5 is a matrix, which seems unstated) -- this used not to be the case. I would prefer
tcn5[tcn %in% -9] <- NA
Using %in% rather than == in computed indices is a good habit to acquire: it also makes things like
tcn5[tcn %in% c(-9, -99)] <- NA
work as expected.
If tcn is a data frame, you have to do this column-by-column, as in
tcn5[] <- lapply(tcn5, function(x) x[x %in% -9] <- NA)
or by a logical index matrix, which is harder to construct.
for(i in 1:dim(tcn5)[2]){ ##for the number of columns
+ for(n in 1:dim(tcn5)[1]){ ##for the number of rows + tcn5[is.na(tcn5[n,i]) | tcn5[n,i] == -9] <- NA + + } + }
-- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595
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