# What's the correct way to align two signals downsampled at 10 Hz?

I'm trying to build a dataset where one of the features is a signal which has originally been sampled at 500 Hz, while another feature is a signal which was sampled at 100 Hz. I want to downsample both of them at 10 Hz and then align them (they start at different times).

What should I do after low-pass filtering them at 5 Hz? And what would be the most correct filter to use?

e.g. I have two signals, signal1 and signal2:

signal1: Sampled at 500 Hz, the first sample is at time signal1_t0. signal2: Sampled at 100 Hz, the first sample is at time signal2_t0.

Once that I have filtered the data as described above, would it be ok to firstly set t0 = max(signal1_t0,signal1_t0) and then get e.g. the closest sample to t0*n + 0.1 from all the samples in the interval (t0*n, t0*n + 0.1) for each signal?

• what does "align all the feautres by sampling them at 10 Hz" mean? Aug 13, 2021 at 16:33
• but yes, if there's no signal of interest above 5 Hz, your method is totally correct and doesn't lose any data. Whether or not it helps "aligning all the features": I don't know :) Aug 13, 2021 at 16:34
• Sorry, I edited the question since I didn't specify the real question which I was trying to ask. Now it should be clearer Aug 13, 2021 at 16:54