Equidistant log scale points I have an x-axis which is in logarithmic scale representing frequency, I would like to have NumPoints on this axis that are equidistant on the log scale, I have the following variables:

Fmin = 100
Fmax = 4000 or 8000
NumPoints = 10

What formula should i use to calculate where the NumPoints-2 points between Fmin and Fmax should go? (Fmin and Fmax should each have a point on them)

Additionally, when i switch from Fmax = 4000 -> 8000 i would like to keep the equidistant points already calculated between Fmin->4000 and add extra points between 4000 and 8000.

Summary

Generate NumPoints between FMan -> Fmax(4000), equidistant on a log scale.
Change Fmax -> 8000
Generate more points between 4000->8000.

Many thanks in advance

Andy
Take the log of your extremities, find your points as if it were on a linear scale beween these extremities, take the exponential of the result.

Example:

The log of your extremities are $\log 100$ and $\log 4000$. Your 10 points on a linear scale between these values would be: $\log 100 + k \frac{\log 4000 - \log 100}{9}$, $k \in \{0, 1, \ldots, 9\}$.

Taking the exponential: $e^{\log 100 + k \frac{\log 4000 - \log 100}{9}}$. Notice that the first and last values are 100 and 4000 as expected.

This works well with linspace in programming languages which have this primitive, for example with python/numpy:

numpy.exp(numpy.linspace(numpy.log(100), numpy.log(4000), 10))


The second part of your question is not clear. To generate more points by preserving the same spacing, continue increasing $k$ above 9.