[antonsoo]

signal[::2] currently keeps the original sampling period, and negative slice starts are treated as literal time offsets. For example, a ten-sample signal starting at 2 s at 4 Hz reports signal[-3:].t_start as 1.25 s instead of 3.75 s.

Normalize the start against the signal length and adjust the sampling rate by direct division for both bare and tuple slices. Add regressions for negative/clipped starts, forward/reverse strides, nested slices and exact sampling-rate preservation. The separate author-list commit follows the first-contribution instructions.

Validation: 634 core tests and 51 subtests pass; Black passes on the changed Python files. On recorded EEGMMIDB S001/R04 data, all 30 slicing configurations match absolute sample-index timestamps after the fix, correcting 18 configurations and 227 event-window selections. All sample values and event-window selections remain correct. Direct rate division avoids the reciprocal-round-trip drift reported in review. This changes __getitem__; the time_slice change in #1905 remains separate.

[zm711]

I have requested @apdavison to help review this.

[apdavison]

This is great, many thanks for catching and fixing this.

I have one suggested improvement - see the inline comments.

[apdavison]

Setting sampling_period here sends the rate through 1/(1/rate), which leads to floating-point problems:

sig = AnalogSignal(..., sampling_rate=25000*pq.Hz)
sig[:].sampling_rate == 25000*pq.Hz
# master: True
# PR:     False   (24999.999999999996)

It would be better to set obj.sampling_rate = self.sampling_rate / step to avoid the conversion.

[apdavison]

Same comment as line 316

[antonsoo]

Changed both slice paths to set sampling_rate = self.sampling_rate / step. The new exact-rate checks cover Hz/kHz units, forward/reverse strides and all three indexing forms. The core suite passes 634 tests and 51 subtests; all 30 recorded EEG slicing cases still match the independent sample-index timestamps and event windows.