[R] transform dataframe with look-up table

[Juan Antonio Balbuena]

   Hello
   I hope that there is a simple solution to this apparently complex problem.
   Any help will be much appreciated:
   I have a dataframe with Left and Right readings (that is, elements in each
   row are paired). For instance,
       Left Right
    [1]  9    8
    [2]  4    3
    [3]  2    1
    [4]  6    5
    [5]  3    1
    [6]  4    1
    [7]  3    2
    [8]  4    2
    [9]  10   8
   [10]  9   10
   I  need  to  produce a new data frame where the values are transformed
   according to a look-up table such as
           input    output
    [1]     5      1
    [2]    10     1
    [3]     4      2
    [4]     8      3
    [5]     6      5
    [6]     5      6
    [7]     7      6
    [8]     2      7
    [9]     9      7
   [10]    10    7
   [11]     2     8
   So  [1, ] in the new dataframe would be 7 3. Quite simple so far, but what
   makes things complicated is the multiple outputs for a single input. In this
   example, 10 corresponds to 1 and 7 so [9, ] in the input dataframe must
   yield two rows in its output counterpart: 1 3 and 7 3. Likewise the output
   for  [10, ] should be 7 1 and 7 7. In addition, given that 3 and 1 are
   missing as inputs the output for [5, ] should be NA NA.
   Thank you very much for your time.
   Juan Antonio Balbuena

   --

   Dr. Juan A. Balbuena
   Marine Zoology Unit
   Cavanilles Institute of Biodiversity and Evolutionary Biology
   University of
   Valencia
   [1]http://www.uv.es/~balbuena
   P.O. Box 22085
   [2]http://www.uv.es/cavanilles/zoomarin/index.htm
   46071 Valencia, Spain
   [3]http://cetus.uv.es/mullpardb/index.html
   e-mail: [4]j.a.balbuena at uv.es    tel. +34 963 543 658    fax +34 963 543 733
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References

   1. http://www.uv.es/%7Ebalbuena
   2. http://www.uv.es/cavanilles/zoomarin/index.htm
   3. http://cetus.uv.es/mullpardb/index.html
   4. mailto:j.a.balbuena at uv.es