Replacing element of a matrix

How to replace every n th element of matrix with some number

matrix has vertical shape

and is single row matrix

Answer 1

[Rik]

I suspect this is homework, so I'm only going to give you a suggestion:

You should have a look at the colon operator and how you can assign values to an array with indexing.

2:4

ans = 1×3

2 3 4

A=rand(1,5);
A(4)=5

A = 1×5

0.2997 0.3387 0.0137 5.0000 0.4140