How do I create an array with unequal increment?

I want to design a program to create an array of numbers. The user can input the maximum and minimum values and the scaling factor.

For example,

max=256,

min=2,

scaling factor=2.

The array will be [2 4 8 16 32 64 128 256].

Is there anyway I can create such array with the max, min and scaling factor as variables? I tried doing it with the following code. However, the x(count) only gives me 1 number instead of storing the answers from the loop.

Is this the right direction to do it? Or is there any other codes to do it in a more efficient way?

Thanks!

xmax=256;
xmin=2;
xfact=2;
count=0;
x=0;
if x<=xmax
count=count+1;
x(count)=x*xfact;
end

Answer 1

[Star Strider]

Try this:

expspace = @(vmin,vmax,inc) vmin * inc.^(0:( log(vmax/vmin)/log(inc)));

vmin =   2;
vmax = 256;
inc =    2;

v = expspace(vmin, vmax, inc)

v =
     2     4     8    16    32    64   128   256

It is also robust to other combinations of input arguments.

Answer 2

[Birdman]

a=2;%min
n=8;%max
r=2;%scaling factor
s = a*r.^(0:n-1)

[Wing]

Thanks! But I want the max to be the last number in the array. In the code you gave me, the input of maximum value is 8 instead of 265.

[Jan]

@Wing: While the input n is 8, the last element of the output is 256 as wanted.

[Stephen23]

"In the code you gave me, the input of maximum value is 8 instead of 265."

The last value is a*r.^(n-1), where a=2, r=2, and n=8, giving 2*2.^(8-1), which is equal to 2^8, which gives 256 (and is exactly what you requested in your question).

[Wing]

Yes, but I would like the last element to be what the input is. so the input of the max number is = the last element. I understand what you mean but the max number that is input into the program might not necessarily be 2^i. For example, min=2, max=199, scaling factor=3, and I want the array to contain the numbers of 2*3, 2*3*3, 2*3*3*3, etc. Sorry for the confusion.