Re: [R] sorting data whilst ignoring NA's

David Winsemius Tue, 09 Mar 2010 10:43:57 -0800


On Mar 9, 2010, at 11:57 AM, emwater wrote:


Hello,

I am very new to R and have hit my first main problem that I hopesomeone

can easily resolve.

I have some data that looks like this (there are 20,000 rows):

qdata

       day month year    flow
  [1,]   2    10 1945      NA
  [2,]   3    10 1945      NA
  [3,]   4    10 1945      NA
  [4,]   5    10 1945      NA
  [5,]   6    10 1945   2.973
  [6,]   7    10 1945      NA
  [7,]   8    10 1945      NA
  [8,]   9    10 1945   2.973
  [9,]  10    10 1945      NA
 [10,]  11    10 1945      NA
 [11,]  12    10 1945      NA
 [12,]  13    10 1945      NA
 [13,]  14    10 1945   2.973
 [14,]  15    10 1945      NA

I want to sort the data in descending order by flow but with all theNA

results sent to the bottom. I have managed to sort the data using:

topflows <- qdata[order(-flow, na.last=TRUE),]


Try (untested):

topflows <- qdata[order(-qdata$flow, na.last=TRUE),]


But this sorts the data by flow value and then year I think giving:

day month year   flow
[1,]  14     3 1947 222.40
[2,]  15     3 1947     NA
[3,]  18     3 1947     NA
[4,]  17     3 1947     NA
[5,]  19     3 1947     NA
[6,]  12     3 1947     NA
[7,]  13     3 1947     NA
[8,]  16     3 1947     NA
[9,]  20     3 1947     NA
[10,]  30    11 1946 106.50
[11,]  30     3 1947 105.60
[12,]  29    11 1946     NA
[13,]  11     3 1947     NA
[14,]  22    11 1946  99.96
[15,]  21    11 1946     NA

I want my data to come out like this:
[1,] 14  3  1947  222.3
[2,] 30  11 1946 106.50
[3,] 30  3  1947  105.60
[4,] 22 11 1946  99.96 and so on...


Any help would be greatly valued.

Thanks

Emma



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David Winsemius, MD
West Hartford, CT

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