Hi

Hi I'm happy to see you got this working! I'm curious to know a little more about your application. What signal are you measuring?

The signal source is acceleration from accelerometer. sample rate is 1k hz. I'm planning to analyze motor vibration. And determine "how health" of the motor.

why is the size of your array changing? ... It seems like your input signal is a fixed size, so the FFT output (periodogram / power spectral density) should also be a fixed size.

Actually I do not fixed the input signal size. I designed to allow users choose the range to calculate FFT. It may be 1 second, 10 seconds, or other range, depends on the analysis needs.

Thanks for your reminder about performance. Maybe I will start check the performance impact of non-fixed signal.

BTW This is my tool for calculating FFT `MathNet.Numerics`

gist
I am also very interested in your `Spectrogram`

project.