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Code to fetch summary info from vector

8 messages · stephen sefick, William Dunlap, Jose Iparraguirre +4 more

Benjamin Gillespie
# 
Hi all,

Thanks in advance for any help.

I have a vector "b":

b=c(1,1,1,2,3,4,3,2,1,1,1,1,1,2,3,4,5,4,3.5,3,2,1,1,1)

Imagine b is river flow throughout time.

I would like some code that will generate the following information:

number of individual 'periods' where b>1 (= 2 in this case)
period 1 length = 5, max = 4
period 2 length = 8, max = 5

I can't figure anything useful out.

Thanks,
		
Ben Gillespie
Research Postgraduate
 
School of Geography
University of Leeds
Leeds
LS2 9JT
 
http://www.geog.leeds.ac.uk/
stephen sefick
# 
I don't know if I understand what you want.  What are the periods?  I 
suspect this is a time series.  What have you tried that didn't work?
kind regards,

Stephen
On 01/15/2013 10:16 AM, Benjamin Gillespie wrote:

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      William Dunlap
    

    

      
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I don't completely understand the  question, but if you are looking
for the lengths of the runs of values greater than 1 then rle() would
help:
  > b <- c(1,1,1,2,3,4,3,2,1,1,1,1,1,2,3,4,5,4,3.5,3,2,1,1,1)
  > r <- rle(b>1)
  > r
  Run Length Encoding
    lengths: int [1:5] 3 5 5 8 3
    values : logi [1:5] FALSE TRUE FALSE TRUE FALSE
  > r$lengths[r$values]
  [1] 5 8
To get the maximum of each run of values greater than one, something
like the following may do (there are more elegant ways, but I don't want
to spend the time on it until I know what the question is):
  > runNumber <- cumsum( c(b[1]>1, (b[-1]>1) & (b[-length(b)]<=1)) )
  > runNumber[b<=1] <- NA
  > tapply(b, runNumber, max)
  1 2 
  4 5

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com

            

      
      
      
    

        

      
      
    

  
  


  


      

    

    

      
      

        


  

        

      Jose Iparraguirre
    

    

      
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Hi Ben

I'm not sure whether I understood correctly, but is it something like this?

            

      
      
      
    

        
[1] 4

            

      
      
      
    

        
[1] 4

            

      
      
      
    

        
[1] 13

            

      
      
      
    

        
[1] 9
Etc...

Jos?

Jos? Iparraguirre
Chief Economist
Age UK



-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of Benjamin Gillespie
Sent: 15 January 2013 16:16
To: r-help at r-project.org
Subject: [R] Code to fetch summary info from vector

Hi all,

Thanks in advance for any help.

I have a vector "b":

b=c(1,1,1,2,3,4,3,2,1,1,1,1,1,2,3,4,5,4,3.5,3,2,1,1,1)

Imagine b is river flow throughout time.

I would like some code that will generate the following information:

number of individual 'periods' where b>1 (= 2 in this case)
period 1 length = 5, max = 4
period 2 length = 8, max = 5

I can't figure anything useful out.

Thanks,
		
Ben Gillespie
Research Postgraduate
 
School of Geography
University of Leeds
Leeds
LS2 9JT
 
http://www.geog.leeds.ac.uk/
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      Jessica Streicher
    

    

      
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Maybe rle can help a little here

rle(b>1)

Run Length Encoding
  lengths: int [1:5] 3 5 5 8 3
  values : logi [1:5] FALSE TRUE FALSE TRUE FALSE

 r<-rle(b>1)

r$lengths[r$values]
[1] 5 8

# started for the maximum but need to go home now, sorry. Will continue tomorrow if noone else finishes it.
groups <- rep(1:length(r$lengths),r$lengths)

        
On 15.01.2013, at 17:16, Benjamin Gillespie wrote:

        

            

      
      
      
    

        

      
      
    

  
  


  


      

    

    

      
      

        


  

        

      Benjamin Gillespie
    

    

      
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Thanks everyone,

I've used the code Will supplied - this worked well.

Thanks to all the others who contributed.

Ben Gillespie
Research Postgraduate

School of Geography
University of Leeds
Leeds
LS2 9JT

Tel: +44(0)113 34 33345
Mob: +44(0)770 868 7641
http://www.geog.leeds.ac.uk/

        

      
      
    

  
  


  


      

    

    

      
      

        


  

        

      Rui Barradas
    

    

      
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Hello,

Continuing Jessica's code, to get the maximum of each group just use

b <- c(1,1,1,2,3,4,3,2,1,1,1,1,1,2,3,4,5,4,3.5,3,2,1,1,1)
r <- rle(b > 1)
groups <- rep(1:length(r$lengths),r$lengths)

tapply(b, groups, FUN = max)

# To get just the groups where b > 1,

mx <- tapply(b, groups, FUN = max)
mx[mx > 1]

# And you can combine both like in

cbind(length = r$lengths[r$values], max = mx[mx > 1])


Hope this helps,

Rui Barradas
Em 15-01-2013 16:57, Jessica Streicher escreveu:

            

      
      
      
    

        

      
      
    

        

      
      
    

  
  


  


      

    

    

      
      

        


  

        

      David Winsemius
    

    

      
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On Jan 15, 2013, at 8:16 AM, Benjamin Gillespie wrote:

        

            

      
      
      
    

        
Look at:

rle(b>1)
?rle

Should get you started.