Velocity threshold identification of saccades
VTI_saccade.RdUse the velocity threshold algorithm from Salvucci & Goldberg (1996) to determine saccadic eye movements. Returns a summary of the saccades found per trial, including start and end coordinates, timing, duration, mean velocity, and peak velocity.
Arguments
- data
A dataframe with raw data (time, x, y, trial) for one participant
- sample_rate
sample rate of the eye-tracker. If default of NULL, then it will be computed from the timestamp data and the number of samples
- threshold
velocity threshold (degrees of VA / sec) to be used for identifying saccades
- minDur
minimum duration (ms) expected for saccades. This helps to avoid identification of very short saccades occuring at the boundary of velocity threshold
Examples
VTI_saccade(example_raw_sac[example_raw_sac$trial<=10,])
#> trialNumber sac_n start end duration origin_x origin_y terminal_x
#> 1 1 1 227 277 50 892.2850 532.7300 156.2932
#> 2 1 2 460 523 63 226.1151 499.5046 1459.3134
#> 3 1 3 630 653 23 1491.4453 494.5910 1752.0873
#> 4 2 1 227 283 56 892.2656 541.0739 192.1308
#> 5 2 2 763 840 77 173.7718 520.9121 1541.3770
#> 6 3 1 160 217 57 913.1104 545.6854 152.2252
#> 7 3 2 1093 1120 27 1692.0314 553.0065 1266.2649
#> 8 4 1 283 340 57 935.8781 530.3051 131.5811
#> 9 4 2 696 730 34 128.5837 523.6625 618.0759
#> 10 5 1 246 296 50 1010.6296 542.1412 1706.7832
#> 11 5 2 653 690 37 1672.3358 546.2828 973.2900
#> 12 6 1 197 247 50 841.1113 534.1552 177.3586
#> 13 6 2 590 620 30 173.2091 523.7553 748.6539
#> 14 7 1 180 220 40 760.8648 535.6373 205.1067
#> 15 7 2 554 574 20 218.5966 527.2309 529.1069
#> 16 8 1 174 230 56 913.3894 547.4196 190.8072
#> 17 8 2 574 657 83 171.3734 509.5301 1661.4254
#> 18 9 1 170 230 60 898.6670 544.0779 151.9758
#> 19 9 2 477 567 90 193.5306 521.3675 1662.9927
#> 20 10 1 194 250 56 882.5818 540.6511 207.0548
#> 21 10 2 540 627 87 180.0508 524.4571 1650.8567
#> terminal_y mean_velocity peak_velocity
#> 1 501.7069 366.2823 456.5382
#> 2 485.6333 488.4571 648.8721
#> 3 550.6735 284.5512 346.2462
#> 4 509.7467 309.1363 445.3536
#> 5 519.1016 445.2093 589.4391
#> 6 523.3356 337.3887 490.4680
#> 7 630.4558 470.6155 773.2718
#> 8 519.0336 357.9397 462.2791
#> 9 596.0885 433.1852 699.4864
#> 10 539.4524 351.2853 463.7055
#> 11 570.9793 495.2926 846.3831
#> 12 525.5338 328.2392 436.6294
#> 13 492.8537 462.8836 668.5812
#> 14 525.2300 344.0023 451.4492
#> 15 674.4199 537.9353 697.1391
#> 16 527.3348 318.2145 471.2241
#> 17 552.5213 448.7033 612.8071
#> 18 530.6465 311.5706 415.2190
#> 19 546.2215 408.7111 594.9715
#> 20 527.9641 297.9789 412.7535
#> 21 563.3275 423.4526 604.0540