Use 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.
Usage
saccade_VTI(
data,
sample_rate = NULL,
threshold = 150,
min_dur = 20,
participant_ID = "participant_ID"
)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
- min_dur
minimum duration (ms) expected for saccades. This helps to avoid identification of very short saccades occurring at the boundary of velocity threshold
- participant_ID
the variable that determines the participant identifier. If no column present, assumes a single participant
Details
It can take either single participant data or multiple participants where there is a variable for unique participant identification.
The function looks for an identifier named participant_ID by default and will treat this as multiple-participant data as default,
if not it is handled as single participant data, or the participant_ID needs to be specified
Examples
data <- combine_eyes(HCL)
saccade_VTI(data, participant_ID = "pNum")
#> pNum 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 3676 3733 57 947.6657 123.4475 1472.9220
#> 6 118 1 6 4223 4279 56 1517.9491 759.8224 973.0053
#> 7 118 1 7 5343 5383 40 928.6512 492.2177 551.4663
#> 8 118 1 8 6792 6826 34 524.8298 829.4756 916.6670
#> 9 118 1 9 7106 7129 23 1008.0858 598.3720 1031.5074
#> 10 118 1 10 7602 7639 37 890.4656 644.2127 524.1420
#> 11 118 1 11 9295 9335 40 573.7701 847.7756 925.2699
#> 12 118 1 12 10435 10489 54 929.5371 135.1185 618.2629
#> 13 118 1 13 10705 10738 33 590.4193 758.2291 945.4900
#> 14 118 1 14 12138 12192 54 977.1132 436.3669 1473.5748
#> 15 118 1 15 12972 13025 53 1538.2589 820.1288 980.1268
#> 16 118 2 1 366 399 33 1009.5214 634.7551 1433.6206
#> 17 118 2 2 1146 1196 50 1488.0968 803.8687 1011.9555
#> 18 118 2 3 1793 1819 26 940.0593 177.6297 931.9980
#> 19 118 2 4 1989 2029 40 899.9465 504.8037 502.1575
#> 20 118 2 5 2626 2679 53 503.8431 787.9458 927.8132
#> 21 118 2 6 3106 3129 23 951.3465 175.7282 971.6648
#> 22 118 2 7 5142 5189 47 990.5532 289.0873 1440.6756
#> 23 118 2 8 5339 5395 56 1439.0196 846.2477 520.0998
#> 24 118 2 9 6235 6285 50 891.8324 167.0562 475.0865
#> 25 118 2 10 6752 6789 37 519.1636 786.9284 939.9464
#> 26 118 2 11 7209 7255 46 989.1180 467.5686 1513.2444
#> 27 118 2 12 7635 7662 27 1513.4448 779.3846 1131.6693
#> 28 118 3 1 933 983 50 1002.7010 194.4611 1485.5097
#> 29 118 3 2 1200 1260 60 1476.1744 841.7218 499.3671
#> 30 118 3 3 1826 1866 40 504.8058 792.4104 896.1292
#> 31 118 3 4 2993 3039 46 996.6983 498.0212 1529.1658
#> 32 118 3 5 3553 3586 33 1453.7949 842.5720 1005.8556
#> 33 118 4 1 160 196 36 981.6367 811.0610 1404.6870
#> 34 118 4 2 540 583 43 1488.3788 767.7919 1037.8731
#> 35 118 4 3 1066 1120 54 932.6748 180.0326 492.1770
#> 36 118 4 4 2389 2443 54 1472.4171 833.8392 637.4518
#> 37 118 4 5 3353 3399 46 529.1758 794.9559 975.5111
#> 38 118 4 6 4156 4189 33 980.6287 176.0979 1218.9348
#> 39 118 4 7 4196 4216 20 1260.4098 660.6613 1388.2071
#> 40 118 4 8 5459 5506 47 529.8645 768.2352 845.4405
#> 41 118 4 9 6166 6216 50 988.4912 480.0328 1513.9437
#> 42 118 4 10 8009 8072 63 1482.7134 866.4826 505.3686
#> 43 118 4 11 8609 8669 60 595.8946 909.1639 1486.6987
#> 44 118 4 12 8915 8969 54 1493.1766 844.0545 946.8369
#> 45 118 5 1 169 193 24 920.7457 793.6681 665.0876
#> 46 118 5 2 436 469 33 647.7492 768.7432 907.6719
#> 47 118 5 3 766 786 20 907.0568 491.8643 820.8612
#> 48 118 5 4 1059 1113 54 600.8392 824.8404 1462.8866
#> 49 118 5 5 1666 1703 37 1495.7123 778.3008 1060.7272
#> 50 118 5 6 2606 2652 46 964.1227 348.4754 1476.4087
#> 51 118 5 7 2996 3036 40 1529.3674 791.3107 1017.8775
#> 52 118 5 8 3682 3739 57 947.3045 301.1887 1499.1632
#> 53 118 5 9 3926 3979 53 1489.7973 768.8057 957.5302
#> 54 118 6 1 323 343 20 771.3237 683.6370 950.7294
#> 55 118 6 2 577 630 53 964.7887 466.5898 1466.3880
#> 56 118 6 3 1160 1216 56 1447.6491 814.8381 544.1528
#> 57 118 6 4 1526 1580 54 549.6498 756.5507 929.6189
#> 58 118 6 5 2823 2843 20 949.0222 189.3002 933.8608
#> 59 118 6 6 3763 3819 56 1453.7815 824.7820 533.1560
#> 60 118 6 7 4286 4323 37 498.8213 790.8234 925.9516
#> 61 119 1 1 419 439 20 937.4859 596.6131 959.2361
#> 62 119 1 2 963 1009 46 926.6087 448.9321 408.7369
#> 63 119 1 3 1386 1419 33 445.2828 730.4440 774.1377
#> 64 119 1 4 1566 1586 20 821.7980 493.3183 961.6049
#> 65 119 1 5 1859 1886 27 987.8758 332.9815 982.6170
#> 66 119 1 6 2066 2102 36 1008.7884 584.3139 1449.6108
#> 67 119 1 7 3022 3089 67 1475.4953 753.0909 454.0886
#> 68 119 1 8 3292 3326 34 473.3284 717.6178 948.4116
#> 69 119 1 9 4159 4205 46 937.9460 474.0402 483.8080
#> 70 119 1 10 4655 4715 60 505.6226 779.1145 1494.9923
#> 71 119 1 11 5005 5059 54 1433.3890 760.0195 592.4676
#> 72 119 1 12 7301 7371 70 531.4111 724.3928 1471.0353
#> 73 119 1 13 7885 7941 56 1557.4926 706.1470 1031.2273
#> 74 119 1 14 8448 8488 40 940.5212 332.6466 428.2784
#> 75 119 1 15 8848 8901 53 329.9313 650.1681 961.6728
#> 76 119 1 16 9111 9148 37 915.4118 334.5176 506.0964
#> 77 119 1 17 9608 9638 30 491.3408 780.1579 878.9651
#> 78 119 1 18 9984 10024 40 913.6017 468.3063 431.8043
#> 79 119 2 1 160 196 36 930.1504 786.8685 506.3560
#> 80 119 2 2 563 626 63 507.0262 754.6377 1422.9613
#> 81 119 2 3 1086 1123 37 1536.6883 737.5674 1171.5084
#> 82 119 2 4 2969 2999 30 958.4742 287.2842 936.6324
#> 83 119 2 5 3216 3249 33 904.4740 653.2866 534.9389
#> 84 119 2 6 3563 3602 39 529.6488 744.3024 943.8313
#> 85 119 2 7 4002 4026 24 935.2114 349.1000 813.9743
#> 86 119 2 8 4216 4256 40 741.5883 472.8151 527.5179
#> 87 119 2 9 4462 4522 60 565.8551 782.8804 1449.5204
#> 88 119 3 1 187 220 33 929.6976 731.8546 491.3072
#> 89 119 3 2 667 727 60 499.3447 755.1829 1465.4223
#> 90 119 3 3 1167 1197 30 1388.1631 659.8787 1009.4100
#> 91 119 3 4 2226 2280 54 1083.8245 440.7186 1366.5362
#> 92 119 3 5 3113 3180 67 1499.9854 787.7492 475.7855
#> 93 119 3 6 3929 3993 64 448.9802 745.1622 1460.1439
#> 94 119 3 7 4989 5069 80 1359.4973 693.7878 484.6122
#> 95 119 3 8 5093 5119 26 446.2522 690.6419 394.5154
#> 96 119 3 9 5692 5742 50 451.1674 677.6303 1005.6018
#> 97 119 3 10 7135 7162 27 933.4311 313.1571 735.9905
#> 98 119 3 11 7365 7405 40 858.5582 358.8731 506.7146
#> 99 119 4 1 237 270 33 926.5049 725.0489 514.1258
#> 100 119 4 2 1390 1440 50 553.2898 758.5523 1410.9398
#> 101 119 4 3 1853 1896 43 1400.3527 761.2807 959.3316
#> 102 119 4 4 2993 3026 33 410.2407 759.6056 834.9296
#> 103 119 4 5 3256 3296 40 878.8572 486.6256 511.0056
#> 104 119 4 6 4143 4199 56 545.5005 791.4970 1429.2845
#> 105 119 4 7 5416 5479 63 1449.6049 722.3000 503.8289
#> 106 119 4 8 6066 6119 53 538.4092 777.9468 1352.3635
#> 107 119 4 9 6625 6682 57 1457.5757 735.3299 509.4560
#> 108 119 4 10 7355 7405 50 455.0061 766.4567 1029.1588
#> 109 119 4 11 7749 7769 20 962.0985 371.5052 975.0627
#> 110 119 4 12 8605 8625 20 961.2967 482.5752 946.2679
#> 111 119 5 1 214 250 36 929.7282 740.4175 495.4903
#> 112 119 5 2 1100 1160 60 562.2012 777.7919 1469.1228
#> 113 119 5 3 2193 2227 34 1623.7868 783.7612 1626.5978
#> 114 119 5 4 2397 2450 53 1624.6249 782.5055 1623.9142
#> 115 119 5 5 2470 2523 53 1626.5158 776.7604 1624.3390
#> 116 119 5 6 2720 2796 76 1575.6467 801.0315 580.4435
#> 117 119 5 7 2890 2916 26 434.0244 734.8002 448.7737
#> 118 119 5 8 3386 3453 67 487.2023 770.7846 1445.4084
#> 119 119 5 9 4503 4569 66 1305.5712 789.1685 518.6549
#> 120 119 5 10 5519 5596 77 559.5449 750.5246 1466.2904
#> 121 119 5 11 6606 6679 73 1538.5927 769.7452 531.8304
#> 122 119 5 12 7395 7429 34 561.1405 727.3658 929.0725
#> 123 119 5 13 8215 8235 20 959.0783 363.6570 1002.1730
#> 124 119 5 14 9009 9055 46 966.1764 181.1402 490.9862
#> 125 119 5 15 9565 9592 27 514.3670 682.0681 863.4544
#> 126 119 5 16 10575 10615 40 863.9232 536.9596 477.5950
#> 127 119 5 17 11755 11798 43 431.9173 762.7475 895.9795
#> 128 119 5 18 12374 12401 27 928.1233 339.4489 708.4844
#> 129 119 6 1 590 626 36 893.5909 421.1214 445.4796
#> 130 119 6 2 3053 3106 53 456.9632 729.2448 1304.1947
#> 131 119 6 3 4232 4262 30 1372.3698 735.7928 1024.0037
#> 132 119 6 4 6778 6818 40 1008.7615 446.5270 1449.8786
#> 133 119 6 5 6832 6852 20 1556.7990 621.5306 1709.8604
#> 134 119 6 6 6938 6965 27 1635.7978 766.4061 1625.8207
#> 135 119 6 7 7558 7588 30 1524.0060 686.7242 1142.0919
#> 136 119 6 8 9365 9415 50 1000.8005 293.0768 1397.7841
#> 137 119 6 9 10281 10344 63 1419.5092 783.3005 522.3444
#> 138 119 6 10 11021 11084 63 495.6926 799.3568 1323.7945
#> 139 119 6 11 11581 11644 63 1488.0635 757.2932 501.3444
#> 140 119 6 12 11994 12021 27 469.7133 707.4822 724.9794
#> 141 119 6 13 12034 12064 30 775.1127 552.5540 998.6819
#> terminal_y mean_velocity peak_velocity
#> 1 808.04272 271.9532 395.7753
#> 2 572.85360 316.5920 453.7707
#> 3 815.95874 386.7776 625.4370
#> 4 362.66265 302.3138 469.6868
#> 5 773.01410 373.9121 676.8416
#> 6 344.40579 314.7485 528.4388
#> 7 811.74409 305.4745 450.6908
#> 8 655.82093 318.2262 433.7030
#> 9 628.36295 460.4057 812.9176
#> 10 812.66139 276.6097 385.5759
#> 11 507.11854 309.7302 482.2899
#> 12 687.51196 299.9637 550.8891
#> 13 500.89552 335.5719 483.3650
#> 14 820.45975 294.7687 432.9660
#> 15 421.15891 332.1922 555.8305
#> 16 800.74046 337.8767 533.4778
#> 17 458.93763 318.9492 498.2116
#> 18 480.38578 287.1814 412.1397
#> 19 806.82680 318.0042 479.7854
#> 20 253.97420 320.5905 509.3843
#> 21 465.01123 297.8809 535.7321
#> 22 817.47684 376.6990 686.0879
#> 23 853.99013 410.2389 646.1997
#> 24 749.27484 362.9380 583.7279
#> 25 510.38435 337.0882 479.3545
#> 26 806.21239 334.0144 496.1255
#> 27 548.60528 403.7822 626.4858
#> 28 811.01401 392.0890 704.2891
#> 29 866.36876 401.5779 668.3855
#> 30 493.93989 304.9522 498.1127
#> 31 836.79907 347.8760 522.6585
#> 32 514.52377 491.4800 940.5552
#> 33 807.59300 287.3825 541.8139
#> 34 407.89316 340.6554 549.7072
#> 35 849.41309 372.2013 682.3726
#> 36 817.06385 392.8085 562.5873
#> 37 465.23668 302.2570 451.3590
#> 38 623.21881 377.0819 638.6894
#> 39 770.51439 226.2203 292.2432
#> 40 270.38513 326.4600 500.7555
#> 41 882.37852 333.2056 522.7518
#> 42 889.74747 390.3220 594.0075
#> 43 885.09883 368.2253 499.7923
#> 44 416.29324 325.8066 519.8207
#> 45 815.40923 265.9251 344.8632
#> 46 460.19167 309.7295 547.4358
#> 47 647.49100 241.5283 265.7954
#> 48 881.41554 400.7040 551.7459
#> 49 485.14086 362.5891 579.1255
#> 50 741.68104 347.3329 581.8454
#> 51 393.74462 402.1167 560.6416
#> 52 815.85457 333.5643 677.8157
#> 53 181.31785 376.0806 501.2942
#> 54 494.17258 323.8532 437.7212
#> 55 819.45070 296.7403 452.0023
#> 56 813.94843 399.1708 565.9836
#> 57 311.93170 282.9525 419.5553
#> 58 411.30941 272.0811 352.7944
#> 59 830.62670 407.5171 590.5819
#> 60 578.07589 319.1983 476.3223
#> 61 385.89048 260.8953 343.8812
#> 62 736.63587 324.2774 434.0907
#> 63 522.73404 296.5318 410.3950
#> 64 332.33636 256.0837 426.6870
#> 65 557.67814 223.6286 327.9540
#> 66 731.04919 319.9811 429.1243
#> 67 723.96569 383.1361 491.0976
#> 68 530.82351 382.8111 588.1953
#> 69 726.20847 288.4276 374.5740
#> 70 785.48033 415.0122 528.3873
#> 71 525.59939 473.6426 742.8217
#> 72 765.71968 341.4174 457.7553
#> 73 277.11461 313.4577 436.7043
#> 74 636.55022 375.6691 498.8435
#> 75 303.23776 341.8446 621.9124
#> 76 685.16739 370.4457 452.0933
#> 77 529.08806 391.1792 552.1682
#> 78 724.13881 351.3465 460.8725
#> 79 762.26611 297.4935 426.7753
#> 80 771.04969 357.9907 445.1150
#> 81 521.52158 286.4167 397.0264
#> 82 584.14036 274.3038 406.9902
#> 83 773.08285 292.4531 498.8591
#> 84 234.80312 402.1033 593.3929
#> 85 447.56302 184.9454 226.6153
#> 86 786.49801 255.0448 324.1577
#> 87 750.54686 375.2577 507.5032
#> 88 758.72776 333.8274 429.9159
#> 89 706.53287 406.8794 550.7194
#> 90 416.62787 388.8453 489.5843
#> 91 692.01373 205.7714 292.9094
#> 92 749.79324 386.7071 502.3280
#> 93 739.73714 407.4949 537.5146
#> 94 624.15468 373.5978 1114.6777
#> 95 683.99888 463.7122 1100.2079
#> 96 446.39116 318.1697 454.1010
#> 97 401.45857 215.1896 328.6196
#> 98 760.78629 334.7032 447.7867
#> 99 746.55221 309.1610 424.0007
#> 100 760.38561 434.7216 571.3466
#> 101 585.73589 319.5020 648.2105
#> 102 477.50542 375.9011 486.5387
#> 103 735.42724 281.9654 427.4536
#> 104 725.27627 391.5986 537.3900
#> 105 750.76249 372.0435 467.7041
#> 106 565.98955 441.9099 787.5928
#> 107 768.40618 426.1481 526.9425
#> 108 449.86136 329.2294 436.9667
#> 109 87.88856 339.0770 511.8123
#> 110 279.86526 303.8552 544.9422
#> 111 735.73645 299.0414 411.5301
#> 112 745.15599 382.9806 476.5716
#> 113 781.91854 211.1565 237.3562
#> 114 780.19254 188.1241 220.3871
#> 115 796.44055 193.7084 304.8210
#> 116 621.57478 385.4126 1038.6576
#> 117 794.40469 535.3712 1213.9914
#> 118 731.99651 362.9122 500.2365
#> 119 771.84247 298.6272 383.4015
#> 120 769.89695 307.2276 425.8958
#> 121 588.35225 431.1572 632.8190
#> 122 426.38805 375.1215 498.1069
#> 123 150.70444 273.7333 373.8756
#> 124 573.53000 340.3861 509.3756
#> 125 402.05052 412.4027 531.6561
#> 126 694.73338 274.6732 385.1506
#> 127 340.18672 366.2587 592.1679
#> 128 422.20742 322.5492 453.1567
#> 129 719.21666 375.4480 457.8041
#> 130 747.38857 415.6465 490.9379
#> 131 514.08373 369.2959 456.5592
#> 132 602.33134 292.4560 343.1387
#> 133 546.70075 507.9605 1342.9012
#> 134 792.84668 230.1979 314.1205
#> 135 403.44032 400.6247 495.2271
#> 136 657.71066 284.3762 403.1224
#> 137 756.58455 353.9641 461.7777
#> 138 779.42050 329.6308 492.5720
#> 139 729.33815 392.7076 497.0189
#> 140 584.69650 264.3671 393.9167
#> 141 409.76345 246.2686 395.0241