Building a new table by repeating elements from another table

Question

I have a small problem that I cannot solve.

I have two tables, one with three elements:

a = {0, L/c, 2L/c};

and the other with 9 elements, all 0:

b = {0, 0, 0, 0, 0, 0, 0, 0, 0};

I would like to put the elements from table a into table b, giving so that I get the following table:

{0, L/c, 2L/c, 0, L/c, 2L/c, 0, L/c, 2L/c}

Can someone please give me some advice?

Do you need b at all or do you simply want to generate a list of n repeated elements? — Yves Klett, Jul 1, 2013 at 7:03

Kuba · Accepted Answer · 2013-07-01 08:23:58Z

4

I don't know if b is something important, but if it is not:

a = {0, L/c, 2 L/c}; 
PadLeft[a, 9, a]

{0, L/c, (2 L)/c, 0, L/c, (2 L)/c, 0, L/c, (2 L)/c}

and if it is:

b = ConstantArray[0, 9];
PadLeft[a, Length@b, a]

{0, L/c, (2 L)/c, 0, L/c, (2 L)/c, 0, L/c, (2 L)/c}

answered Jul 1, 2013 at 8:23

Kuba♦

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bill s · Accepted Answer · 2013-07-01 06:58:15Z

3

a = {0, L/c, 2 L/c};
b = ConstantArray[0, 9];
Flatten[ConstantArray[a, Length[b]/Length[a]]]

Or, even more succinctly:

  b = Flatten[ConstantArray[{0, L/c, 2 L/c}, 3]]

answered Jul 1, 2013 at 6:58

bill s

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$\begingroup$ Just found out. Thank you very much bill $\endgroup$
– de_wight
Jul 1, 2013 at 7:04
1

$\begingroup$ @de_wight, if this answer has solved your problem, you should accept it by clicking on the check mark on the left. $\endgroup$
– m_goldberg
Jul 1, 2013 at 7:36

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2 Answers 2