Downsampling Gradually Increasing Frequency Data While Preserving Ratio

[Chaos_Theory]

I have a dataset of 168 data points, where each data point consists of two columns: frequency and HVSR data. The frequency values range from 0.2 Hz to 30.5259 Hz, and the dataset exhibits a gradually increasing frequency behavior, meaning that at lower frequencies, the frequency increment is slower, and it increases faster at higher frequencies.

My goal is to reduce the dataset to contain only 50 data points while preserving the original frequency range (0.2 Hz to ~30 Hz) and maintaining the gradual increase in frequency (corresponding to the right frequency). How can I perform this downsampling operation while ensuring that the increasing frequency ratio is maintained in the reduced dataset? I can't find the right equations..
I attach a txt file with the data.
Thank you very much in advance.
Regards,
Chaos_Theory.

 

[blamocur]

Your frequencies are very close to geometric progression, which means that their logarithms are evenly spaced. I would use frequency logarithms for resampling, then bring them back to the original domain by using exponents.