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Space-by-time muscle synergy decomposition (sNM3F)

Source: R/emg-spacetime.R
spaceByTimeSynergy.Rd

Decomposes a set of trials' muscle x time EMG into shared SPATIAL synergies (which muscles group together), shared TEMPORAL synergies (when they are active) and a per-trial activation matrix linking them (Delis et al. 2014).

Usage

spaceByTimeSynergy(
  trials,
  n_spatial,
  n_temporal,
  max_iter = 500L,
  tol = 1e-06,
  n_restart = 5L,
  seed = NULL
)

Arguments

trials

A list of muscle x time non-negative matrices (one per trial), or a [muscle, time, trial] array.

n_spatial, n_temporal

Numbers of spatial and temporal synergies.

max_iter, tol

Multiplicative-update iterations and convergence tolerance.

n_restart

Random restarts (best kept; default 5).

seed

Optional RNG seed.

Value

a spacetime_synergy: spatial (muscle x n_spatial), temporal (time x n_temporal), activation (list of n_spatial x n_temporal per trial), vaf, iterations.

References

Delis I, et al. (2014) Front Comput Neurosci 8:118.

See also

muscleSynergy(), tuckerSynergy()

Examples

set.seed(1)
Ws <- matrix(stats::runif(6 * 2), 6, 2); Wt <- matrix(stats::runif(50 * 2), 50, 2)
trials <- lapply(1:10, function(n) Ws %*% (matrix(stats::runif(4), 2, 2)) %*% t(Wt))
fit <- spaceByTimeSynergy(trials, 2, 2, n_restart = 2)
fit$vaf
#> [1] 0.9999996