[R] sorting data whilst ignoring NA's

[emwater]

Hello,

I am very new to R and have hit my first main problem that I hope someone
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 the NA
results sent to the bottom. I have managed to sort the data using: 

topflows <- qdata[order(-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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