Creating a simpsons rule matrix

I want to create a matrix that repeats the numbers 4, 2 for 500 values but has a 1 in the 1st and last spot in each row

for 99 rows

ex: 1 4 2 4 2 4 2 4 ... 4 1

1 4 2 4 2 4 2 4 ... 4 1

1 4 2 4 2 4 2 4 ... 4 1

1 4 2 4 2 4 2 4 ... 4 1

Answer 1

[John D'Errico]

Simple. Just create a matrix that alternates 4, then 2, then 4, etc. Then append a new first and last element of 1 to the result.

So, you could use a tool like repmat to do most of the work. For example:

repmat([4 2],1,4)
ans =
     4     2     4     2     4     2     4     2

See that it will always end with a 2. So, append a 1 at the beginning, and [4 1] at the end.

[1,repmat([4 2],1,4),[4 1]]
ans =
     1     4     2     4     2     4     2     4     2     4     1

As you can see, the above worked simply, and quite well. I could also have used mod to do the heavy work.

v = [1,mod(1:9,2)*2+2,1]
v =
     1     4     2     4     2     4     2     4     2     4     1

Finally, it looks like you want a result that has multiple rows, all the same. Use repmat, replicating one row into many rows!