Use the velocity threshold algorithm from Salvucci & Goldberg (2000) 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 (pID, time, x, y, trial), the standardised raw data form for eyetools
- threshold
velocity threshold (degrees of VA / sec) to be used for identifying saccades
- min_dur
minimum duration (ms) expected for saccades. This helps to avoid identification of very short saccades occurring at the boundary of velocity threshold
References
Salvucci, D. D., & Goldberg, J. H. (2000). Identifying fixations and saccades in eye-tracking protocols. Proceedings of the Symposium on Eye Tracking Research & Applications - ETRA '00, 71–78.
Examples
data <- combine_eyes(HCL)
saccade_VTI(data)
#> pID trial sac_n start end duration origin_x origin_y terminal_x
#> 1 118 1 1 747 790 43 924.8913 502.8802 572.8710
#> 2 118 1 2 1183 1216 33 550.2522 797.0665 904.1434
#> 3 118 1 3 2193 2243 50 1049.3491 235.9011 1507.8226
#> 4 118 1 4 2690 2750 60 1517.8485 787.2293 972.7982
#> 5 118 1 5 3106 3126 20 951.8168 416.6045 1001.7526
#> 6 118 1 6 3676 3733 57 947.6657 123.4475 1472.9220
#> 7 118 1 7 4223 4279 56 1517.9491 759.8224 973.0053
#> 8 118 1 8 5343 5383 40 928.6512 492.2177 551.4663
#> 9 118 1 9 6792 6826 34 524.8298 829.4756 916.6670
#> 10 118 1 10 7106 7132 26 1008.0858 598.3720 1030.8711
#> 11 118 1 11 7602 7639 37 890.4656 644.2127 524.1420
#> 12 118 1 12 9295 9335 40 573.7701 847.7756 925.2699
#> 13 118 1 13 10435 10489 54 929.5371 135.1185 618.2629
#> 14 118 1 14 10702 10738 36 564.5121 785.2703 945.4900
#> 15 118 1 15 12138 12192 54 977.1132 436.3669 1473.5748
#> 16 118 1 16 12972 13025 53 1538.2589 820.1288 980.1268
#> 17 118 2 1 366 399 33 1009.5214 634.7551 1433.6206
#> 18 118 2 2 1146 1196 50 1488.0968 803.8687 1011.9555
#> 19 118 2 3 1793 1823 30 940.0593 177.6297 936.3069
#> 20 118 2 4 1989 2029 40 899.9465 504.8037 502.1575
#> 21 118 2 5 2626 2679 53 503.8431 787.9458 927.8132
#> 22 118 2 6 3106 3129 23 951.3465 175.7282 971.6648
#> 23 118 2 7 5142 5189 47 990.5532 289.0873 1440.6756
#> 24 118 2 8 5339 5395 56 1439.0196 846.2477 520.0998
#> 25 118 2 9 6235 6285 50 891.8324 167.0562 475.0865
#> 26 118 2 10 6752 6789 37 519.1636 786.9284 939.9464
#> 27 118 2 11 7209 7255 46 989.1180 467.5686 1513.2444
#> 28 118 2 12 7635 7662 27 1513.4448 779.3846 1131.6693
#> 29 118 3 1 933 983 50 1002.7010 194.4611 1485.5097
#> 30 118 3 2 1200 1260 60 1476.1744 841.7218 499.3671
#> 31 118 3 3 1826 1870 44 504.8058 792.4104 914.0560
#> 32 118 3 4 2993 3039 46 996.6983 498.0212 1529.1658
#> 33 118 3 5 3553 3586 33 1453.7949 842.5720 1005.8556
#> 34 118 4 1 160 196 36 981.6367 811.0610 1404.6870
#> 35 118 4 2 540 583 43 1488.3788 767.7919 1037.8731
#> 36 118 4 3 1066 1120 54 932.6748 180.0326 492.1770
#> 37 118 4 4 2389 2443 54 1472.4171 833.8392 637.4518
#> 38 118 4 5 3349 3399 50 508.5161 821.9540 975.5111
#> 39 118 4 6 4156 4216 60 980.6287 176.0979 1388.2071
#> 40 118 4 7 5456 5506 50 509.6492 805.8238 845.4405
#> 41 118 4 8 5839 5859 20 950.2765 202.0675 947.2431
#> 42 118 4 9 6166 6219 53 988.4912 480.0328 1530.9120
#> 43 118 4 10 8009 8072 63 1482.7134 866.4826 505.3686
#> 44 118 4 11 8609 8669 60 595.8946 909.1639 1486.6987
#> 45 118 4 12 8915 8969 54 1493.1766 844.0545 946.8369
#> 46 118 5 1 169 193 24 920.7457 793.6681 665.0876
#> 47 118 5 2 436 469 33 647.7492 768.7432 907.6719
#> 48 118 5 3 766 786 20 907.0568 491.8643 820.8612
#> 49 118 5 4 1059 1113 54 600.8392 824.8404 1462.8866
#> 50 118 5 5 1666 1703 37 1495.7123 778.3008 1060.7272
#> 51 118 5 6 2606 2652 46 964.1227 348.4754 1476.4087
#> 52 118 5 7 2996 3036 40 1529.3674 791.3107 1017.8775
#> 53 118 5 8 3682 3739 57 947.3045 301.1887 1499.1632
#> 54 118 5 9 3926 3979 53 1489.7973 768.8057 957.5302
#> 55 118 6 1 323 343 20 771.3237 683.6370 950.7294
#> 56 118 6 2 577 630 53 964.7887 466.5898 1466.3880
#> 57 118 6 3 1156 1216 60 1484.7630 814.1868 544.1528
#> 58 118 6 4 1526 1580 54 549.6498 756.5507 929.6189
#> 59 118 6 5 2823 2843 20 949.0222 189.3002 933.8608
#> 60 118 6 6 3763 3819 56 1453.7815 824.7820 533.1560
#> 61 118 6 7 4286 4323 37 498.8213 790.8234 925.9516
#> 62 119 1 1 419 439 20 937.4859 596.6131 959.2361
#> 63 119 1 2 963 1009 46 926.6087 448.9321 408.7369
#> 64 119 1 3 1386 1419 33 445.2828 730.4440 774.1377
#> 65 119 1 4 1566 1586 20 821.7980 493.3183 961.6049
#> 66 119 1 5 1859 1886 27 987.8758 332.9815 982.6170
#> 67 119 1 6 2066 2102 36 1008.7884 584.3139 1449.6108
#> 68 119 1 7 3022 3089 67 1475.4953 753.0909 454.0886
#> 69 119 1 8 3292 3326 34 473.3284 717.6178 948.4116
#> 70 119 1 9 4159 4205 46 937.9460 474.0402 483.8080
#> 71 119 1 10 4655 4715 60 505.6226 779.1145 1494.9923
#> 72 119 1 11 5005 5059 54 1433.3890 760.0195 592.4676
#> 73 119 1 12 7301 7371 70 531.4111 724.3928 1471.0353
#> 74 119 1 13 7885 7941 56 1557.4926 706.1470 1031.2273
#> 75 119 1 14 8448 8488 40 940.5212 332.6466 428.2784
#> 76 119 1 15 8848 8901 53 329.9313 650.1681 961.6728
#> 77 119 1 16 9111 9148 37 915.4118 334.5176 506.0964
#> 78 119 1 17 9608 9638 30 491.3408 780.1579 878.9651
#> 79 119 1 18 9984 10024 40 913.6017 468.3063 431.8043
#> 80 119 2 1 160 196 36 930.1504 786.8685 506.3560
#> 81 119 2 2 563 626 63 507.0262 754.6377 1422.9613
#> 82 119 2 3 1086 1123 37 1536.6883 737.5674 1171.5084
#> 83 119 2 4 2969 2999 30 958.4742 287.2842 936.6324
#> 84 119 2 5 3216 3249 33 904.4740 653.2866 534.9389
#> 85 119 2 6 3563 3602 39 529.6488 744.3024 943.8313
#> 86 119 2 7 4002 4026 24 935.2114 349.1000 813.9743
#> 87 119 2 8 4216 4256 40 741.5883 472.8151 527.5179
#> 88 119 2 9 4462 4522 60 565.8551 782.8804 1449.5204
#> 89 119 3 1 187 220 33 929.6976 731.8546 491.3072
#> 90 119 3 2 663 727 64 475.6411 761.7902 1465.4223
#> 91 119 3 3 1167 1197 30 1388.1631 659.8787 1009.4100
#> 92 119 3 4 1647 1670 23 956.9901 379.3481 996.2286
#> 93 119 3 5 2226 2280 54 1083.8245 440.7186 1366.5362
#> 94 119 3 6 3113 3180 67 1499.9854 787.7492 475.7855
#> 95 119 3 7 3929 3993 64 448.9802 745.1622 1460.1439
#> 96 119 3 8 4989 5069 80 1359.4973 693.7878 484.6122
#> 97 119 3 9 5093 5119 26 446.2522 690.6419 394.5154
#> 98 119 3 10 5692 5746 54 451.1674 677.6303 1024.6236
#> 99 119 3 11 7135 7162 27 933.4311 313.1571 735.9905
#> 100 119 3 12 7365 7405 40 858.5582 358.8731 506.7146
#> 101 119 4 1 237 270 33 926.5049 725.0489 514.1258
#> 102 119 4 2 1390 1440 50 553.2898 758.5523 1410.9398
#> 103 119 4 3 1853 1896 43 1400.3527 761.2807 959.3316
#> 104 119 4 4 2993 3026 33 410.2407 759.6056 834.9296
#> 105 119 4 5 3256 3296 40 878.8572 486.6256 511.0056
#> 106 119 4 6 4143 4199 56 545.5005 791.4970 1429.2845
#> 107 119 4 7 5416 5479 63 1449.6049 722.3000 503.8289
#> 108 119 4 8 6066 6119 53 538.4092 777.9468 1352.3635
#> 109 119 4 9 6625 6682 57 1457.5757 735.3299 509.4560
#> 110 119 4 10 7355 7405 50 455.0061 766.4567 1029.1588
#> 111 119 4 11 7749 7769 20 962.0985 371.5052 975.0627
#> 112 119 4 12 8605 8625 20 961.2967 482.5752 946.2679
#> 113 119 5 1 214 250 36 929.7282 740.4175 495.4903
#> 114 119 5 2 1100 1160 60 562.2012 777.7919 1469.1228
#> 115 119 5 3 2193 2227 34 1623.7868 783.7612 1626.5978
#> 116 119 5 4 2397 2450 53 1624.6249 782.5055 1623.9142
#> 117 119 5 5 2470 2523 53 1626.5158 776.7604 1624.3390
#> 118 119 5 6 2720 2796 76 1575.6467 801.0315 580.4435
#> 119 119 5 7 2890 2916 26 434.0244 734.8002 448.7737
#> 120 119 5 8 3386 3456 70 487.2023 770.7846 1464.8231
#> 121 119 5 9 4499 4569 70 1337.8185 786.2550 518.6549
#> 122 119 5 10 5519 5596 77 559.5449 750.5246 1466.2904
#> 123 119 5 11 6606 6686 80 1538.5927 769.7452 532.0211
#> 124 119 5 12 7395 7429 34 561.1405 727.3658 929.0725
#> 125 119 5 13 8215 8235 20 959.0783 363.6570 1002.1730
#> 126 119 5 14 9009 9055 46 966.1764 181.1402 490.9862
#> 127 119 5 15 9565 9592 27 514.3670 682.0681 863.4544
#> 128 119 5 16 10575 10615 40 863.9232 536.9596 477.5950
#> 129 119 5 17 11755 11798 43 431.9173 762.7475 895.9795
#> 130 119 5 18 12374 12401 27 928.1233 339.4489 708.4844
#> 131 119 6 1 590 626 36 893.5909 421.1214 445.4796
#> 132 119 6 2 3053 3106 53 456.9632 729.2448 1304.1947
#> 133 119 6 3 4232 4262 30 1372.3698 735.7928 1024.0037
#> 134 119 6 4 6778 6818 40 1008.7615 446.5270 1449.8786
#> 135 119 6 5 6832 6852 20 1556.7990 621.5306 1709.8604
#> 136 119 6 6 6938 6965 27 1635.7978 766.4061 1625.8207
#> 137 119 6 7 7558 7588 30 1524.0060 686.7242 1142.0919
#> 138 119 6 8 9365 9415 50 1000.8005 293.0768 1397.7841
#> 139 119 6 9 10281 10344 63 1419.5092 783.3005 522.3444
#> 140 119 6 10 11021 11084 63 495.6926 799.3568 1323.7945
#> 141 119 6 11 11581 11644 63 1488.0635 757.2932 501.3444
#> 142 119 6 12 11994 12021 27 469.7133 707.4822 724.9794
#> 143 119 6 13 12034 12064 30 775.1127 552.5540 998.6819
#> terminal_y mean_velocity peak_velocity
#> 1 808.04272 283.5040 412.5845
#> 2 572.85360 330.0384 473.0425
#> 3 815.95874 403.2042 651.9966
#> 4 362.66265 315.1539 489.6344
#> 5 182.75663 316.1650 434.0858
#> 6 773.01410 389.7924 705.5829
#> 7 344.40579 328.1166 550.8807
#> 8 811.74409 318.4488 469.8318
#> 9 655.82093 331.7420 452.1227
#> 10 647.37457 443.3985 847.4330
#> 11 812.66139 288.3583 401.9520
#> 12 507.11854 322.8852 502.7726
#> 13 687.51196 312.7039 574.2841
#> 14 500.89552 333.6369 503.8933
#> 15 820.45975 307.2883 451.3544
#> 16 421.15891 346.3010 579.4354
#> 17 800.74046 352.2269 556.1337
#> 18 458.93763 332.4957 519.3703
#> 19 499.25743 284.7993 429.6438
#> 20 806.82680 331.5106 500.1617
#> 21 253.97420 334.2068 531.0173
#> 22 465.01123 310.5326 558.4837
#> 23 817.47684 392.6976 715.2217
#> 24 853.99013 427.6617 673.6405
#> 25 749.27484 378.3523 608.5170
#> 26 510.38435 351.4051 499.7125
#> 27 806.21239 348.2006 517.1956
#> 28 548.60528 420.9308 653.0899
#> 29 811.01401 408.7409 734.1952
#> 30 866.36876 418.6330 696.7679
#> 31 487.25831 306.0391 519.2672
#> 32 836.79907 362.6508 544.8551
#> 33 514.52377 512.3510 980.4846
#> 34 807.59300 299.5884 564.8238
#> 35 407.89316 355.1235 573.0521
#> 36 849.41309 388.0088 711.3487
#> 37 817.06385 409.4915 586.4790
#> 38 465.23668 304.9752 470.5284
#> 39 770.51439 322.6836 665.8114
#> 40 270.38513 328.6062 522.0221
#> 41 452.90632 325.6190 467.3367
#> 42 892.25707 336.0883 544.9523
#> 43 889.74747 406.8992 619.2330
#> 44 885.09883 383.8644 521.0181
#> 45 416.29324 339.6442 541.8968
#> 46 815.40923 277.2199 359.5104
#> 47 460.19167 322.8844 570.6843
#> 48 647.49100 251.7870 277.0848
#> 49 881.41554 417.7221 575.1774
#> 50 485.14086 377.9888 603.7192
#> 51 741.68104 362.0846 606.5546
#> 52 393.74462 419.1947 584.4507
#> 53 815.85457 347.7312 706.5983
#> 54 181.31785 392.0532 522.5838
#> 55 494.17258 337.6080 456.3115
#> 56 819.45070 309.3438 471.1991
#> 57 813.94843 402.1739 590.0195
#> 58 311.93170 294.9704 437.3743
#> 59 411.30941 283.6373 367.7784
#> 60 830.62670 424.8246 615.6619
#> 61 578.07589 332.7554 496.5516
#> 62 385.89048 271.9732 358.4825
#> 63 736.63587 338.0463 452.5216
#> 64 522.73404 309.1227 427.8199
#> 65 332.33636 266.9573 444.8036
#> 66 557.67814 233.1243 341.8791
#> 67 731.04919 333.5676 447.3443
#> 68 723.96569 399.4037 511.9482
#> 69 530.82351 399.0647 613.1668
#> 70 726.20847 300.6745 390.4783
#> 71 785.48033 432.6330 550.8206
#> 72 525.59939 493.7518 774.3539
#> 73 765.71968 355.9139 477.1906
#> 74 277.11461 326.7673 455.2461
#> 75 636.55022 391.6198 520.0229
#> 76 303.23776 356.3590 648.3147
#> 77 685.16739 386.1747 471.2884
#> 78 529.08806 407.7882 575.6108
#> 79 724.13881 366.2645 480.4402
#> 80 762.26611 310.1253 444.8956
#> 81 771.04969 373.1909 464.0138
#> 82 521.52158 298.5782 413.8839
#> 83 584.14036 285.9511 424.2707
#> 84 773.08285 304.8708 520.0391
#> 85 234.80312 419.1758 618.5850
#> 86 447.56302 192.7987 236.2379
#> 87 786.49801 265.8744 337.9217
#> 88 750.54686 391.1909 529.0502
#> 89 758.72776 348.0018 448.1696
#> 90 706.53287 410.5039 574.1005
#> 91 416.62787 405.3553 510.3707
#> 92 120.06360 295.9172 541.4810
#> 93 692.01373 214.5089 305.3467
#> 94 749.79324 403.1262 523.6552
#> 95 739.73714 424.7965 560.3353
#> 96 624.15468 389.4591 1161.9753
#> 97 683.99888 483.3973 1146.8924
#> 98 445.97947 321.0485 473.3812
#> 99 401.45857 224.3269 342.5730
#> 100 760.78629 348.9148 466.7990
#> 101 746.55221 322.2882 442.0032
#> 102 760.38561 453.1791 595.6031
#> 103 585.73589 333.0678 675.7288
#> 104 477.50542 391.8615 507.1958
#> 105 735.42724 293.9378 445.6026
#> 106 725.27627 408.2254 560.2054
#> 107 750.76249 387.8402 487.5617
#> 108 565.98955 460.6720 821.0242
#> 109 768.40618 444.2416 549.3145
#> 110 449.86136 343.2085 455.5196
#> 111 87.88856 353.4739 533.5421
#> 112 279.86526 316.7568 568.0781
#> 113 735.73645 311.7389 429.0032
#> 114 745.15599 399.2416 496.8057
#> 115 781.91854 220.1227 247.4348
#> 116 780.19254 196.1123 229.7452
#> 117 796.44055 201.9337 317.7640
#> 118 621.57478 401.7760 1082.7339
#> 119 794.40469 558.0969 1265.4959
#> 120 733.85336 368.1586 521.4750
#> 121 771.84247 304.1642 399.6805
#> 122 769.89695 320.2727 443.9788
#> 123 627.22944 425.9321 659.6841
#> 124 426.38805 391.0488 519.2551
#> 125 150.70444 285.3563 389.7502
#> 126 573.53000 354.8389 531.0020
#> 127 402.05052 429.9127 554.2282
#> 128 694.73338 286.3361 401.5039
#> 129 340.18672 381.8093 617.3080
#> 130 422.20742 336.2447 472.3969
#> 131 719.21666 391.3893 477.2416
#> 132 747.38857 433.2943 511.7817
#> 133 514.08373 384.9760 475.9437
#> 134 602.33134 304.8740 357.7085
#> 135 546.70075 529.5197 1399.8635
#> 136 792.84668 239.9725 327.4583
#> 137 403.44032 417.6347 516.2530
#> 138 657.71066 296.4511 420.2386
#> 139 756.58455 368.9933 481.3838
#> 140 779.42050 343.6269 513.4852
#> 141 729.33815 409.3816 518.1208
#> 142 584.69650 275.5924 410.6422
#> 143 409.76345 256.7255 411.7965