Generate a numerical series

Hi everyone, I want to generate this vector: 1e-8, 1e-9, 1e-10, 1e-11, 1e-12, 1e-13, 1e-14.

How can i do it?

Thanks

[Torsten]

v=10.^(-(8:14))

Answer 1

[DGM]

This is one way:

k = -8:-1:-14;
v = 10.^k

v = 1×7

1.0e+-8 * 1.0000 0.1000 0.0100 0.0010 0.0001 0.0000 0.0000

fprintf('%g\n',v.') % for sake of clarity

1e-08
1e-09
1e-10
1e-11
1e-12
1e-13
1e-14

Answer 2

[John D'Errico]

While @DGM is correct (+1 from me on that answer, please accept that answer, as it is the correct one), in that it is what I would do immediately, there are always many ways to do things like this. The alternative I can think of immediately is to use cumprod with repmat:

format long g
v = cumprod([1e-8,repmat(0.1,1,6)])

v = 1×7

1.0e+00 * 1e-08 1e-09 1e-10 1e-11 1e-12 1e-13 1e-14

fprintf('%g\n',v.') % for sake of clarity

1e-08
1e-09
1e-10
1e-11
1e-12
1e-13
1e-14

I could also have used cumprod, in conjunction with repelem instead of repmat. That would be slightly less kludgy looking.

cumprod([1e-8,repelem(0.1,6)])'

ans = 7×1

1.0e+00 * 1e-08 1e-09 1e-10 1e-11 1e-12 1e-13 1e-14

Then I think of logspace, which does work nicely. In fact, logspace is a pretty clean looking solution. Still not as obvious in my eyes as that which DGM proposed.

logspace(-8,-14,7).'

ans = 7×1

1.0e+00 * 1e-08 1e-09 1e-10 1e-11 1e-12 1e-13 1e-14

And of course, there is this devious solution:

exp((-8:-1:-14)*log(10)).'

ans = 7×1

1.0e+00 * 9.99999999999998e-09 9.99999999999997e-10 9.99999999999996e-11 9.99999999999998e-12 9.99999999999997e-13 9.99999999999996e-14 9.99999999999999e-15

which is technically correct, exceot that floating point trash appears in the least significant bits. But 9.99999999999999e-9 is technically 1e-8, exept for an error in the least significant bit of the result.

I can stop here, but with some effort, I'd bet there are more.