Hi Folks, I'm trying to find a neat solution to an apparently simple problem, but one which turns out to be a bit more intricate and tricky than one might expect. Suppose I have numbers given to a large number of digits. For example 1234567021 where (though I don't know this beforehand) only the last 3 digits will be varying (and all 3 will vary). What I want is, give a vector x of such numbers, to extract the minimal set of final digits which will include the varying digits (i.e. in this case the last 3 digits). And there may be a decimal point somewhere along the line (though again I won't know where, nor whether). I can think of brute-force ways of doing this, but I'd like a neat one! Best wishes to all, Ted. -------------------------------------------------------------------- E-Mail: (Ted Harding) <Ted.Harding at nessie.mcc.ac.uk> Fax-to-email: +44 (0)870 094 0861 Date: 29-Sep-05 Time: 18:45:26 ------------------------------ XFMail ------------------------------
Select varying LS digits in long numbers?
2 messages · (Ted Harding)
I've received what looks like a good -- and neat! -- solution off-list from Hadley Wickham. Suppose "numbers" is a vector of
long integers. Then Hadley wrote:
digits <- outer(numbers, 10:0,
function(x,y) numbers %/% 10^y %% 10)
apply(digits,2, function(x) length(unique(x)))
This certainly looks cast-iron, and nicely passes my "slipperiness"
test:
numbers<-c(1234566999,1234567001)
digits <- outer(numbers, 10:0, function(x,y) numbers %/% 10^y %% 10)
result<-apply(digits,2, function(x) length(unique(x))); result
# [1] 1 1 1 1 1 1 1 2 2 2 2
d1<-min(which(result>1)); d1
# [1] 8
numbers%%(10^(12-d1))
# [1] 6999 7001
as desired!
Thanks also to Patrick Burns and Jim Holtman for other suggestions
based (in effect) on diff(range(numbers)).
On 29-Sep-05 Ted Harding wrote:
Hi Folks, I'm trying to find a neat solution to an apparently simple problem, but one which turns out to be a bit more intricate and tricky than one might expect. Suppose I have numbers given to a large number of digits. For example 1234567021 where (though I don't know this beforehand) only the last 3 digits will be varying (and all 3 will vary). What I want is, give a vector x of such numbers, to extract the minimal set of final digits which will include the varying digits (i.e. in this case the last 3 digits). And there may be a decimal point somewhere along the line (though again I won't know where, nor whether). I can think of brute-force ways of doing this, but I'd like a neat one! Best wishes to all, Ted. -------------------------------------------------------------------- E-Mail: (Ted Harding) <Ted.Harding at nessie.mcc.ac.uk> Fax-to-email: +44 (0)870 094 0861 Date: 29-Sep-05 Time: 18:45:26 ------------------------------ XFMail ------------------------------
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-------------------------------------------------------------------- E-Mail: (Ted Harding) <Ted.Harding at nessie.mcc.ac.uk> Fax-to-email: +44 (0)870 094 0861 Date: 29-Sep-05 Time: 22:35:15 ------------------------------ XFMail ------------------------------