Sort matrix according to first column in R

Question

I have a matrix with two columns of the following form   1 349 1 393 1 392 4 459 3 49 3 32 2 94   I would like to sort this matrix in increasing order based on the first column but I would like to keep the corresponding values in the second column   The output would look like this   1 349 1 393 1 392 2 94 3 49 3 32 4 459

User · Answer

If your data is in a matrix named foo  the line you would run is   foo sorted foo order foo  1

User · Answer

Be aware that if you want to have values in the reverse order  you can easily do so    gt  example   matrix c 1 1 1 4 3 3 2 349 393 392 459 49 32 94   ncol   2   gt  example order example  1   decreasing   TRUE           1    2   1      4  459  2      3   49  3      3   32  4      2   94  5      1  349  6      1  393  7      1  392

User · Answer

Creating a data table with key V1 automatically does this for you  Using Stephan s data foo   gt  require data table   gt  foo dt  lt - data table foo  key  V1    gt  foo dt    V1  V2 1   1 349 2   1 393 3   1 392 4   2  94 5   3  49 6   3  32 7   4 459

User · Answer

The accepted answer works like a charm unless you re applying it to a vector  Since a vector is non-recursive  you ll get an error like this     operator is invalid for atomic vectors   You can use   in that case  foo order foo  V1

User · Answer

Read the data   foo  lt - read table text  1 349   1 393   1 392   4 459   3 49   3 32   2 94     And sort   foo order foo V1      This relies on the fact that order keeps ties in their original order  See  order

[r] Sort matrix according to first column in R

Examples related to r