How do I multiples of a number in an array

How do I create array with following properties: For the first row, each element is 8 times the corresponding element of x. For the second row, each element is 2 times the square of the corresponding element of x followed by a subtraction 1.

Answer 1

[DGM]

Depends how far you want to go with it. You could leverage implicit array expansion to do it in a way that might make a more general solution a bit easier.

x = 1:10;
k = [8; 2];
p = [1; 2];
a = [0; 1];

A = k.*x.^p - a

A = 2×10

8 16 24 32 40 48 56 64 72 80 1 7 17 31 49 71 97 127 161 199

[Emmanuel Lebile]

Job welldone.Thanks

[dpb]

I had thought of polyval but was/is unfortunate it isn't internally vectorized --

x=1:3;
b=[0 8 0;2 0 -1];

>> [polyval(b(1,:),x);polyval(b(2,:),x)]
ans =
          8.00         16.00         24.00
          1.00          7.00         17.00
>> cell2mat(arrayfun(@(i)polyval(b(i,:),x),1:size(b,1),'uni',0).')
ans =
          8.00         16.00         24.00
          1.00          7.00         17.00
>> 

Answer 2

[dpb]

Well, what have you tried? Follow the recipe given --

y=[8x;2*x.^2-1];  % x is vector

If size(x) --> 2,N, then will need to subscript the above appropriately or clarify what the definition really means.