Finding row index containing maximum value using R

Question

Given the following matrix lets assume I want to find the maximum value in column two   mat  lt - matrix c 1 3 7 9 4 6   byrow   T  nc   3  mat        1    2    3   1      1    2    3  2      7    8    9  3      4    5    6   I know max mat  2   will return 8  How can I return the row index  in this case row two

User · Answer

See  order   You just need the last index  or first  in decreasing order   so this should do the trick   order matrix  2  decreasing T  1

User · Answer

How about the following  where y is the name of your matrix and you are looking for the maximum in the entire matrix    row y  y  max y     if you want to extract the row   y row y  y  max y       this returns unsorted rows    To return sorted rows use   y sort row y  y  max y        The advantage of this approach is that you can change the conditional inside to anything you need   Also  using col y  and location of the hanging comma you can also extract columns   y  col y  y  max y      To find just the row for the max in a particular column  say column 2 you could use   seq along y  2   y  2   max y  2      again the conditional is flexible to look for different requirements   See Phil Spector s excellent  An introduction to S and S-Plus  Chapter 5 for additional ideas

User · Answer

See  which max   gt  which max  matrix  2     1  2

[r] Finding row index containing maximum value using R

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