roboto.analytics.signal_similarity
Submodules
Package Contents
Match
A subsequence of a target signal that is similar to a query signal.
Attributes
Match.distance
Measure of similarity between a query signal and the subsequence of the target signal this Match represents. A smaller distance indicates a closer match.
In single-scale search (scale=None) this is the raw z-normalised Euclidean distance produced by MASS, with range [0, 2·√N] where N is the query length.
In multi-scale search (scale provided) this is multiplied by √N / √M (where N is the original needle length and M is the resampled length at that scale step), projecting onto the same [0, 2·√N] range as single-scale search. This means a max_distance threshold calibrated on single-scale search transfers directly to multi-scale search without adjustment.
Match.scale
The time-scale factor at which this match was found.
A value of 1.0 means the matched subsequence has the same length as the query. Values greater than 1.0 mean the matched subsequence is proportionally longer (the action occurred more slowly in the target than in the query). Values less than 1.0 mean the matched subsequence is proportionally shorter (the action occurred more quickly).
This field is only meaningful when scale is passed to find_similar_signals().
Match.subsequence
The subsequence of the target signal this Match represents. It is equivalent to target[start_idx:end_idx].
Match.to_event()
Create a Roboto Platform event out of this similarity match result.
Parameters
Return type
MatchContext
Correlate a matched subsequence back to its source.
Scale
Configuration for rate-invariant (multi-scale) signal similarity search.
Searching across multiple scales finds a query pattern regardless of how quickly or slowly it unfolds in the target. For example, a robot lifting a cup in 1 second and the same robot lifting a cup in 3 seconds would both be found.
min and max are positive scale factors relative to the original query length. A scale of 1.0 corresponds to the original query length; 2.0 searches for target subsequences twice as long (action happened at half speed); 0.5 searches for subsequences half as long (action happened at double speed).
While Scale.any() provides a convenient wide-range preset, providing domain-informed bounds (e.g. Scale(min=0.5, max=3.0) for a motion that can happen between half and triple speed) will both improve match quality — by concentrating the search grid where matches are physically plausible — and reduce compute by avoiding unnecessary scale steps.
Scale.any()
Well-known preset covering a wide range of speed ratios (0.1x to 10x).
Return type
Scale.factors()
Return a list of scale factors spanning the configured range.
Return type
Attributes
Scale.spacing
How to distribute scale values across the range.
"log"(default) — geometrically spaced; equal ratio between adjacent steps, which is more natural for speed ratios (e.g. 0.5x, 1x, 2x are equally spaced on a log scale)."linear"— linearly spaced.
find_similar_signals()
Find subsequences of topic data (from haystack) that are similar to needle.
If needle is a dataframe with a single, non-index column, single-dimensional similarity search will be performed. If it instead has multiple non-index columns, multi-dimensional search will be performed.
Even if there is no true similarity between the query signal and a topic’s data, this will always return at least one Match. Matches are expected to improve in quality as the topic data is more relevant to the query. Matches are returned sorted in ascending order by their distance, with the best matches (lowest distance) first.
If max_distance is provided, only matches with a distance less than max_distance will be returned. Given distances computed against all comparison windows in the target, this defaults to the maximum of: 1. the minimum distance 2. the mean distance minus two standard deviations
Use max_matches_per_topic to limit the number of match results contributed by a single topic.
If normalize is True, values will be projected to the unit scale before matching. This makes the search amplitude-invariant (y-axis): it matches the shape of the signal regardless of its absolute magnitude. For example, a query sequence of [1., 2., 3.] will perfectly match (distance == 0) the target [1000., 2000., 3000.] if normalize is True, but would have a distance of nearly 3800 if normalize is False.
DataFrames with string-typed columns are supported as long as all values are convertible to numeric types (e.g., "1.0"). Rows containing values that cannot be converted are dropped with a warning.
Rate-invariant (multi-scale) search
Pass a Scale to make the search rate-invariant (x-axis / time axis): it finds the query pattern regardless of how quickly or slowly it unfolds in the target. For example, a robot lifting a cup in 1 second and the same robot lifting a cup in 3 seconds would both be found with an appropriate scale.
See Scale for details on configuring the scale range, step count, and spacing. Well-known presets are available as class attributes, e.g. Scale.any().
The scale at which each match was found is reported in scale.
When scale is used, max_matches_per_topic is applied to the combined results across all scales for a given topic, keeping the best (lowest-distance) matches.
Distance normalisation in multi-scale mode
The raw z-normalised Euclidean distance produced by MASS has range [0, 2·√M], where M is the query length at a given scale. Without correction this biases results toward smaller scales (shorter queries always produce smaller raw distances).
When scale is used, every distance is multiplied by √N / √M before being stored in distance, where N is the original needle length. This projects all scales onto the same [0, 2·√N] range — identical to the single-scale range — so that distances are directly comparable across scales and consistent with single-scale results. A max_distance threshold tuned on single-scale search can therefore be reused without adjustment in multi-scale search.
Single-scale distances (scale=None) are unchanged.
Parameters
needle pandas.haystack collections.max_distance Optional[float]max_matches_per_topic Optional[int]normalize boolscale Optional[roboto.Return type