[R] using string variable as order() function argument

[jim holtman]

Try this:

> mytable
  id col1 col2 col3
1 10    0    4    8
2 11    1    2    2
3 12    0    8    3
4 13    0    5    5
> colName <- 'col3'
> mytable[order(mytable[[colName]]),]
  id col1 col2 col3
2 11    1    2    2
3 12    0    8    3
4 13    0    5    5
1 10    0    4    8
> colName <- 'id'
> mytable[order(mytable[[colName]]),]
  id col1 col2 col3
1 10    0    4    8
2 11    1    2    2
3 12    0    8    3
4 13    0    5    5
>



On Mon, Jul 26, 2010 at 2:54 PM, mirek wyczesany
<miroslaw.wyczesany at uj.edu.pl> wrote:
> Hello,
>
> In my script I would like to use a loop, which sorts the dataframe according
> to different columns, pointed by the string variable.
>
>    id col1  col2  col3
> 1   10    0    4      8
> 2   11    1    2      2
> 3   12    0    8      3
> 4   13    0    5      5
>
> Usually the order() function can be used like this:
>
> sorted = mytable**[order(column3) , ]
>
> which results in properly sorted table:
> **
>
>    id col1  col2  col3
> 2   11    1    2      2
> 3   12    0    8      3
> 4   13    0    5      5
> 1   10    0    4      8
>
> **But when trying to use a string variable instead of "column3" name:
>
> columnname = "column3"
> **sorted = mytable**[order(columnname) , ]**
>
> this command is not properly evaluated and the effect is somewhat strange.
>
> Would you suggest some solution?
>
> Thanks a lot!
>
> Mirek
>
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-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?