I have two matrices:

Matrix1 = 
  Table[NumberForm[N[(10 i + 9 j)/70, 3], {4, 2}], {i, 33}, {j, 18}];


Matrix2 = 
  Table[NumberForm[N[(12 i + 17 j)/70, 3], {4, 2}], {i, 33}, {j, 13}];


I want to "interleave" the first column of Matrix 1 horizontally with all the columns of Matrix 2. Then the second column of Matrix 1 with all the columns of Matrix 2; and continue like this until the last column of Matrix 1 has been interleaved with all the columns of Matrix 2. The following is my attempt to do this; here I have only gone as far as interleaving the first six columns of Matrix 1 with all the columns of Matrix 2; (I stopped at 6 for decorum sake...)

Table[{Matrix1[[i]][[1]], Matrix2[[i]][[1]], Matrix1[[i]][[1]], 
   Matrix2[[i]][[2]], Matrix1[[i]][[1]], Matrix2[[i]][[3]], 
   Matrix1[[i]][[1]], Matrix2[[i]][[4]], Matrix1[[i]][[1]], 
   Matrix2[[i]][[5]], Matrix1[[i]][[1]], Matrix2[[i]][[6]], 
   Matrix1[[i]][[1]], Matrix2[[i]][[7]], Matrix1[[i]][[1]], 
   Matrix2[[i]][[8]], Matrix1[[i]][[1]], Matrix2[[i]][[9]], 
   Matrix1[[i]][[1]], Matrix2[[i]][[10]], Matrix1[[i]][[1]], 
   Matrix2[[i]][[11]], Matrix1[[i]][[1]], Matrix2[[i]][[12]], 
   Matrix1[[i]][[1]], Matrix2[[i]][[13]], Matrix1[[i]][[2]], 
   Matrix2[[i]][[1]], Matrix1[[i]][[2]], Matrix2[[i]][[2]], 
   Matrix1[[i]][[2]], Matrix2[[i]][[3]], Matrix1[[i]][[2]], 
   Matrix2[[i]][[4]], Matrix1[[i]][[2]], Matrix2[[i]][[5]], 
   Matrix1[[i]][[2]], Matrix2[[i]][[6]], Matrix1[[i]][[2]], 
   Matrix2[[i]][[7]], Matrix1[[i]][[2]], Matrix2[[i]][[8]], 
   Matrix1[[i]][[2]], Matrix2[[i]][[9]], Matrix1[[i]][[2]], 
   Matrix2[[i]][[10]], Matrix1[[i]][[2]], Matrix2[[i]][[11]], 
   Matrix1[[i]][[2]], Matrix2[[i]][[12]], Matrix1[[i]][[2]], 
   Matrix2[[i]][[13]], Matrix1[[i]][[3]], Matrix2[[i]][[1]], 
   Matrix1[[i]][[3]], Matrix2[[i]][[2]], Matrix1[[i]][[3]], 
   Matrix2[[i]][[3]], Matrix1[[i]][[3]], Matrix2[[i]][[4]], 
   Matrix1[[i]][[3]], Matrix2[[i]][[5]], Matrix1[[i]][[3]], 
   Matrix2[[i]][[6]], Matrix1[[i]][[3]], Matrix2[[i]][[7]], 
   Matrix1[[i]][[3]], Matrix2[[i]][[8]], Matrix1[[i]][[3]], 
   Matrix2[[i]][[9]], Matrix1[[i]][[3]], Matrix2[[i]][[10]], 
   Matrix1[[i]][[3]], Matrix2[[i]][[11]], Matrix1[[i]][[3]], 
   Matrix2[[i]][[12]], Matrix1[[i]][[3]], Matrix2[[i]][[13]], 
   Matrix1[[i]][[4]], Matrix2[[i]][[1]], Matrix1[[i]][[4]], 
   Matrix2[[i]][[2]], Matrix1[[i]][[4]], Matrix2[[i]][[3]], 
   Matrix1[[i]][[4]], Matrix2[[i]][[4]], Matrix1[[i]][[4]], 
   Matrix2[[i]][[5]], Matrix1[[i]][[4]], Matrix2[[i]][[6]], 
   Matrix1[[i]][[4]], Matrix2[[i]][[7]], Matrix1[[i]][[4]], 
   Matrix2[[i]][[8]], Matrix1[[i]][[4]], Matrix2[[i]][[9]], 
   Matrix1[[i]][[4]], Matrix2[[i]][[10]], Matrix1[[i]][[4]], 
   Matrix2[[i]][[11]], Matrix1[[i]][[4]], Matrix2[[i]][[12]], 
   Matrix1[[i]][[4]], Matrix2[[i]][[13]], Matrix1[[i]][[5]], 
   Matrix2[[i]][[1]], Matrix1[[i]][[5]], Matrix2[[i]][[2]], 
   Matrix1[[i]][[5]], Matrix2[[i]][[3]], Matrix1[[i]][[5]], 
   Matrix2[[i]][[4]], Matrix1[[i]][[5]], Matrix2[[i]][[5]], 
   Matrix1[[i]][[5]], Matrix2[[i]][[6]], Matrix1[[i]][[5]], 
   Matrix2[[i]][[7]], Matrix1[[i]][[5]], Matrix2[[i]][[8]], 
   Matrix1[[i]][[5]], Matrix2[[i]][[9]], Matrix1[[i]][[5]], 
   Matrix2[[i]][[10]], Matrix1[[i]][[5]], Matrix2[[i]][[11]], 
   Matrix1[[i]][[5]], Matrix2[[i]][[12]], Matrix1[[i]][[5]], 
   Matrix2[[i]][[13]], Matrix1[[i]][[6]], Matrix2[[i]][[1]], 
   Matrix1[[i]][[6]], Matrix2[[i]][[2]], Matrix1[[i]][[6]], 
   Matrix2[[i]][[3]], Matrix1[[i]][[6]], Matrix2[[i]][[4]], 
   Matrix1[[i]][[6]], Matrix2[[i]][[5]], Matrix1[[i]][[6]], 
   Matrix2[[i]][[6]], Matrix1[[i]][[6]], Matrix2[[i]][[7]], 
   Matrix1[[i]][[6]], Matrix2[[i]][[8]], Matrix1[[i]][[6]], 
   Matrix2[[i]][[9]], Matrix1[[i]][[6]], Matrix2[[i]][[10]], 
   Matrix1[[i]][[6]], Matrix2[[i]][[11]], Matrix1[[i]][[6]], 
   Matrix2[[i]][[12]], Matrix1[[i]][[6]], Matrix2[[i]][[13]]}, {i, 1, 
   33}] // MatrixForm

Thank you for your help!

  • $\begingroup$ Transpose@Riffle[Transpose@Matrix1, Transpose@Matrix2] ? $\endgroup$
    – george2079
    Aug 26, 2016 at 18:40
  • $\begingroup$ To George2079; your command riffles the two matrices but, it is not interleaving them in the manner that I described above. Notice that the first column of Matrix 1 is interleaved with each column of Matrix 2. Next the second column of Matrix 1 is interleaved with each column of Matrix 2; etc. ; until the last column of Matrix 1 is interleaved with each column of Matrix 2. Thank you for your attempt though! $\endgroup$ Aug 26, 2016 at 18:57
  • $\begingroup$ can you make a smaller example so you can show the whole result? What are the dimensions of the result? $\endgroup$
    – george2079
    Aug 26, 2016 at 19:14

1 Answer 1


Possible approaches with Riffle:

dim1 = Last@Dimensions[Matrix1];
dim2 = Last@Dimensions[Matrix2];
tMatrix2 = Transpose[Matrix2];

Transpose[Join @@ 
   (Riffle[ConstantArray[Matrix1[[All, #]], dim2], tMatrix2] & /@ Range[dim1])


      Join @@ (ConstantArray[#, Last@Dimensions[Matrix2]] & /@ Transpose[Matrix1]), 
      {2, -1, 2}]

An approach with Outer:

Transpose[Join @@ Outer[Sequence, Transpose[Matrix1], Transpose[Matrix2], 1]]
  • $\begingroup$ Thank you Xavier (and thank you George)! Indeed that last code does exactly what I need! Thanks! $\endgroup$ Aug 26, 2016 at 19:43

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