Convert a matrix to a 1 dimensional array

Question

I have a matrix  32X48    How can I convert the matrix into a single dimensional array

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Simple and fast since a 1d array is essentially a vector  vector  lt - array 1 length array

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you can use as vector    It looks like it is the fastest method according to my little benchmark  as follows   library microbenchmark  x matrix runif 1e4  100 100    generate a 100x100 matrix microbenchmark y lt -as vector x  y lt -x 1 length x   y lt -array x  y lt -c x  times 1e4    The first solution uses as vector    the second uses the fact that a matrix is stored as a contiguous array in memory and length m  gives the number of elements in a matrix m  The third instantiates an array from x  and the fourth uses the concatenate function c    I also tried unmatrix from gdata  but it s too slow to be mentioned here   Here are some of the numerical results I obtained    gt  microbenchmark          y lt -as vector x           y lt -x 1 length x            y lt -array x           y lt -c x           times 1e4   Unit  microseconds                 expr    min      lq     mean  median      uq       max neval    y  lt - as vector x   8 251 13 1640 29 02656 14 4865 15 7900 69933 707 10000  y  lt - x 1 length x   59 709 70 8865 97 45981 73 5775 77 0910 75042 933 10000        y  lt - array x   9 940 15 8895 26 24500 17 2330 18 4705  2106 090 10000            y  lt - c x  22 406 33 8815 47 74805 40 7300 45 5955  1622 115 10000   Flattening a matrix is a common operation in Machine Learning  where a matrix can represent the parameters to learn but one uses an optimization algorithm from a generic library which expects a vector of parameters  So it is common to transform the matrix  or matrices  into such a vector  It s the case with the standard R function optim

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If you instead had a data frame  df  that had multiple columns and you want to vectorize you can do  as matrix df  ncol 1

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From  matrix   A matrix is the special case of a two-dimensional  array     You can simply change the dimensions of the matrix array   Elts int  lt - as matrix tmp int     read table returns a data frame as Brandon noted dim Elts int   lt -  maxrow int maxcol int 1

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Either read it in with  scan   or just do as vector   on the matrix  You might want to transpose the matrix first if you want it by rows or columns     gt  m matrix 1 12 3 4   gt  m        1    2    3    4   1      1    4    7   10  2      2    5    8   11  3      3    6    9   12  gt  as vector m    1   1  2  3  4  5  6  7  8  9 10 11 12  gt  as vector t m     1   1  4  7 10  2  5  8 11  3  6  9 12

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try c    x   matrix 1 9  ncol   3   x        1    2    3   1      1    4    7  2      2    5    8  3      3    6    9  c x    1  1 2 3 4 5 6 7 8 9

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array A  or array t A   will give you a 1-d array

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It might be so late  anyway here is my way in converting Matrix to vector   library gdata  vector data lt - unmatrix yourdata byrow T     hope that will help

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You can use Joshua s solution but I think you need Elts int  lt - as matrix tmp int   Or for loops    z  lt - 1    Initialize counter  lt - 1    Initialize for y in 1 48       Assuming 48 columns otherwise  swap 48 and 32 for  x in 1 32      z counter   lt - tmp int x y  counter  lt - 1   counter       z is a 1d vector

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If we re talking about data frame  then you should ask yourself are the variables of the same type  If that s the case  you can use rapply  or unlist  since data frames are lists  deep down in their souls      data mtcars   unlist mtcars   rapply mtcars  c    completely stupid and pointless  and slower

[arrays] Convert a matrix to a 1 dimensional array

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