[R] sorting data whilst ignoring NA's

[David Winsemius]

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 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),]

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
>
>
>
> -- 
> View this message in context: http://n4.nabble.com/sorting-data-whilst-ignoring-NA-s-tp1586277p1586277.html
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>
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David Winsemius, MD
West Hartford, CT