How do I write this matrix?

Question

The following code gives 20 data as output.

How can I make a 5*4 matrix by that data list?

Check out Table, and don't forget to capitalize Sin and Cos. — Chris K, Nov 04 '18 at 15:11
Please post code in code blocks in the future. This is not copyable. I think this will answer all your questions: Why avoid For — Szabolcs, Nov 04 '18 at 15:23
Hi a-b, when Szabolcs asks for code, he means text that can be copy-pasted. The only way we can fix problems is if we can reproduce them! — bill s, Nov 04 '18 at 15:48

FredrikD · Answer 1 · 2018-11-04T16:10:50.497

5

Here is a starting point without the For loops:

Clear@f; 
f[i_, j_] /; OddQ[j] := c[i, j]; 
f[i_, j_] /; EvenQ[j] := s[i, j]; 

n1 = 2; 
res = Table[f[i, j], {i, -n1, n1}, {j, 1, 2*n1}]; 

(* Note MatrixForm is for presentation, not for computations *)
    res // MatrixForm

You can then enter your definition of c and s

edited Nov 04 '18 at 16:10

answered Nov 04 '18 at 15:59

FredrikD

1,868
1
13
25

2

Oh please, leave away MatrixForm. It is the cause for so many desperate questions on this forum... (still +1). – Henrik Schumacher Nov 04 '18 at 16:07
Good point! I added a comment above to separate the calculated result from the presentation. – FredrikD Nov 04 '18 at 16:09

score 4 · Answer 2 · answered Nov 04 '18 at 15:56

4

n = 2;
Table[
 If[OddQ[j],
  Cos[2. Pi i j/(2 n + 1)],
  Sin[2. Pi i j/(2 n + 1)]
  ],
 {i, -n, n}, {j, 1, 2 n}
 ]

answered Nov 04 '18 at 15:56

Henrik Schumacher

106,770
7
179
309

2

+1 Or slightly shorter Table[If[OddQ[j], Cos, Sin][2. Pi i j/(2 n + 1)], {i, -n, n}, {j, 2 n}] – Bob Hanlon Nov 04 '18 at 18:19

How do I write this matrix?

2 Answers2