[R] Looping, Control Flow & Conditional Statements
Charles C. Berry
cberry at tajo.ucsd.edu
Fri Jun 13 17:59:52 CEST 2008
See
?rle
Start with this:
> a1.runs <- rle( a1 )
> a1.runs$lengths[ a1.runs$values>0 ]
[1] 3 4
>
HTH,
Chuck
p.s.
> library(fortunes)
> fortune(106)
If the answer is parse() you should usually rethink the question.
-- Thomas Lumley
R-help (February 2005)
--
see
?get
On Fri, 13 Jun 2008, Garth.Warren at csiro.au wrote:
> Dear R Group:
>
>
>
> I have little experience using R and even less experience with control
> flow type questions.
>
>
>
> See the following code:
>
>
>
> a1 = c(0, 1, 1, 1,
>
> 0, 0, 0, 0, 0,
>
> 0, 0, 1,
>
> 1, 1, 1, 0, 0)
>
>
>
> for(i in 1:1){
>
> sx <- paste("a",i,sep="")
>
> s <- eval(parse(text = paste("a",i,sep="")))
>
> {g = numeric(length(s))
>
> k = numeric(length(s))
>
> {for (i in 1:length(s))
>
> {for (j in 1:length(s))
>
> ifelse(((j=i)>1),(g[j] = s[j] + s[i]),(k[j] = s[j] + s[i]))
>
> }}
>
> h1 <- hist(g,freq=TRUE)
>
> h <- h1$counts[4]
>
> cat(sx,":", h,"\n",file = "C:/temp/test-beta.txt", append=TRUE)
>
> }}
>
>
>
>
>
> The output is:
>
>> g
>
> [1] 0 2 2 2 0 0 0 0 0 0 0 2 2 2 2 0 0
>
>> k
>
> [1] 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
>
>>
>
>> h
>
> [1] 7
>
>
>
> & a text file, which has:
>
> a1 : 7
>
>
>
> k is a by-product of the ifelse statement and is of no interest & g and
> h only go part-way to answering my question, which is:
>
>
>
> For every time an object i.e. a1 (which is actually a time series) - 0 1
> 1 1 0 0 0 0 0 0 0 1 1 1 1 0 0 has as value over 0 how long do the
> values stay above 0. So in this case a1 has two goups or events where
> the value is above zero, the first event lasts for 3 'days' and the
> second event lasts for 4 'days'. I have my code telling me that there
> was a total of 7 'days' in event or above 0, but what I need to know is
> that there were two 'events' and the 1st lasted 3 'days' and the 2nd
> lasted '4' days. Essentially I want a text file output to say:
>
>
> a1.1 : 3
>
>
> a1.2 : 4
>
>
>
> My thinking is that I need to somehow get the code working through each
> vector one value at a time and when a value is found to meet the critera
> of > 0 R creates a new vector; to use the above example it would come
> to the first value >0 and then create the new vector a1.1 = (1,1,1) then
> as the next value in the series is 0 it would close this new vector
> 'a1.1'. It would then continue until it reaches the next value >0 and
> then create the vector a1.2 = (1,1,1,1) then again as the next value in
> the series is 0 it would close this new vector, and so on.
>
>
>
> Then all I need to do is perform a count of '1's in these new vectors to
> find how many days they met this criteria of being greater than 0
>
>
>
> I hope the above makes sense and I really hope there is someone willing
> and able to help. I don't know how to proceed.
>
>
>
> Thanks,
>
> Garth
>
>
>
>
>
>
>
>
>
>
>
>
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>
> [[alternative HTML version deleted]]
>
> ______________________________________________
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
Charles C. Berry (858) 534-2098
Dept of Family/Preventive Medicine
E mailto:cberry at tajo.ucsd.edu UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/ La Jolla, San Diego 92093-0901
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