Why is expand.grid in R returning <0 rows>?

February 25, 2022

I’m trying to use expand.grid to eventually plot estimates from a statistical model. But the output is:

[1] ID     Age    Sex    Tcoded
<0 rows> (or 0-length row.names)

code:

new_df <- with(test,
               expand.grid(ID = factor(levels(ID)[1], levels = levels(ID)),
                           Age = gratia::seq_min_max(Age, n = 100),
                           Sex = factor(levels(Sex), levels = levels(Sex)),
                           Tcoded = median(Tcoded)))

If I remove the first line for ID, the function works.
Why is this happening?

sample data:

structure(list(ID = c(33714L, 35377L, 40556L, 40798L, 40800L, 
40815L, 50848L, 52183L, 52461L, 53320L, 53873L, 54206L, 54581L, 
55122L, 55267L, 55462L, 55612L, 55920L, 56022L, 56307L, 56420L, 
56679L, 57405L, 57480L, 57725L, 57809L, 58004L, 58215L, 58229L, 
59326L, 59327L, 59865L, 60099L, 60100L, 60280L, 60384L, 60429L, 
60493L, 60503L, 60603L, 60664L, 60846L, 61415L, 61749L, 61883L, 
62081L, 62983L, 63327L, 63329L, 64418L, 64507L, 64596L, 65178L, 
65250L, 65802L, 65975L, 65978L, 66396L, 66572L, 66589L, 74034L, 
74427L, 74607L, 74952L, 75732L, 76574L, 76595L, 76755L, 76759L, 
77203L, 77453L, 77668L, 81064L, 81065L, 33714L, 35377L, 40556L, 
40798L, 40800L, 40815L, 50848L, 52183L, 52461L, 53320L, 53873L, 
54206L, 54581L, 55122L, 55267L, 55462L, 55612L, 55920L, 56022L, 
56307L, 56420L, 56679L, 57405L, 57480L, 57725L, 57809L, 58004L, 
58215L, 58229L, 59326L, 59327L, 59865L, 60099L, 60100L, 60280L, 
60384L, 60429L, 60493L, 60503L, 60603L, 60664L, 60846L, 61415L, 
61749L, 61883L, 62081L, 62983L, 63327L, 63329L, 64418L, 64507L, 
64596L, 65178L, 65250L, 65802L, 65975L, 65978L, 66396L, 66572L, 
66589L, 74034L, 74427L, 74607L, 74952L, 75732L, 76574L, 76595L, 
76755L, 76759L, 77203L, 77453L, 77668L, 81064L, 81065L, 33714L, 
35377L, 40556L, 40798L, 40800L, 40815L, 50848L, 52183L, 52461L, 
53320L, 53873L, 54206L, 54581L, 55122L, 55267L, 55462L, 55612L, 
55920L, 56022L, 56307L, 56420L, 56679L, 57405L, 57480L, 57725L, 
57809L, 58004L, 58215L, 58229L, 59326L, 59327L, 59865L, 60099L, 
60100L, 60280L, 60384L, 60429L, 60493L, 60503L, 60603L, 60664L, 
60846L, 61415L, 61749L, 61883L, 62081L, 62983L, 63327L, 63329L, 
64418L, 64507L, 64596L, 65178L, 65250L, 65802L, 65975L, 65978L, 
66396L, 66572L, 66589L, 74034L, 74427L, 74607L, 74952L, 75732L, 
76574L, 76595L, 76755L, 76759L, 77203L, 77453L, 77668L, 81064L, 
81065L), Sex = structure(c(1L, 2L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 1L, 2L, 1L, 2L, 2L, 1L, 2L, 
2L, 1L, 2L, 1L, 1L, 2L, 2L, 1L, 1L, 1L, 2L, 2L, 2L, 1L, 1L, 2L, 
2L, 1L, 2L, 1L, 1L, 1L, 2L, 2L, 2L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 2L, 2L, 2L, 2L, 2L, 1L, 1L, 2L, 1L, 1L, 1L, 2L, 1L, 2L, 1L, 
1L, 1L, 2L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 2L, 2L, 1L, 2L, 1L, 2L, 2L, 1L, 2L, 2L, 1L, 2L, 1L, 1L, 2L, 
2L, 1L, 1L, 1L, 2L, 2L, 2L, 1L, 1L, 2L, 2L, 1L, 2L, 1L, 1L, 1L, 
2L, 2L, 2L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 
1L, 1L, 2L, 1L, 1L, 1L, 2L, 1L, 2L, 1L, 1L, 1L, 2L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 1L, 2L, 1L, 
2L, 2L, 1L, 2L, 2L, 1L, 2L, 1L, 1L, 2L, 2L, 1L, 1L, 1L, 2L, 2L, 
2L, 1L, 1L, 2L, 2L, 1L, 2L, 1L, 1L, 1L, 2L, 2L, 2L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 1L, 1L, 2L, 1L, 1L, 1L, 
2L, 1L, 2L, 1L, 1L), .Label = c("Male", "Female"), class = "factor"), 
    Age = c(15L, 15L, 9L, 11L, 16L, 9L, 16L, 16L, 14L, 8L, 6L, 
    14L, 10L, 15L, 13L, 15L, 8L, 9L, 9L, 8L, 9L, 9L, 13L, 10L, 
    7L, 8L, 8L, 6L, 15L, 8L, 11L, 14L, 12L, 10L, 16L, 12L, 10L, 
    6L, 13L, 11L, 12L, 13L, 10L, 13L, 14L, 12L, 17L, 9L, 12L, 
    11L, 10L, 12L, 10L, 10L, 14L, 16L, 15L, 14L, 14L, 13L, 10L, 
    12L, 9L, 9L, 16L, 10L, 14L, 15L, 13L, 15L, 13L, 13L, 8L, 
    11L, 16L, 16L, 11L, 13L, 18L, 10L, 18L, 18L, 15L, 10L, 8L, 
    15L, 12L, 16L, 14L, 16L, 9L, 11L, 11L, 10L, 10L, 11L, 14L, 
    12L, 8L, 9L, 9L, 8L, 16L, 9L, 13L, 16L, 13L, 12L, 18L, 13L, 
    11L, 8L, 14L, 12L, 13L, 14L, 11L, 14L, 15L, 14L, 18L, 11L, 
    14L, 12L, 12L, 13L, 11L, 11L, 15L, 17L, 16L, 15L, 15L, 14L, 
    11L, 13L, 10L, 11L, 18L, 11L, 15L, 16L, 14L, 17L, 14L, 14L, 
    9L, 12L, 18L, 18L, 12L, 14L, 19L, 11L, 19L, 19L, 16L, 11L, 
    9L, 17L, 13L, 18L, 16L, 18L, 11L, 12L, 12L, 11L, 11L, 12L, 
    16L, 13L, 9L, 11L, 10L, 9L, 17L, 11L, 14L, 17L, 14L, 13L, 
    19L, 15L, 12L, 9L, 15L, 14L, 14L, 15L, 12L, 16L, 17L, 15L, 
    20L, 12L, 15L, 13L, 13L, 14L, 12L, 12L, 16L, 19L, 18L, 16L, 
    16L, 15L, 12L, 14L, 11L, 11L, 19L, 12L, 16L, 17L, 15L, 18L, 
    15L, 15L, 10L, 13L), Mean_DTI = c(-3.91040964443843, -4.1357309415226, 
    -3.15711439697149, -5.3057953682613, -5.64125379300701, -5.14501797062188, 
    0.244858660867345, 0.0760011434854038, -1.38050716781916, 
    -0.765398953185992, -1.47720169386702, -1.64309892713909, 
    -0.396819316883117, -1.36975793945299, -1.80785572309015, 
    -0.401914887891913, -0.811404680008261, -2.4492910546021, 
    -0.620903118150862, -1.10304119407832, -0.683772758549858, 
    -1.47159656575735, -0.823876696667884, 0.229547683217108, 
    -1.91347963071532, -1.05594355918274, -2.37962731952471, 
    -1.34893889218848, -0.385827442278431, -0.980092345023242, 
    -0.181058281596406, -0.832975930612162, -1.9959308225624, 
    -0.12787022611412, -0.205371434695515, -0.609353157197594, 
    -0.477183751078979, -1.53245224237668, -0.137187841673061, 
    -1.11978378453579, -1.38506891710323, -0.665622819909006, 
    -0.858065551674517, -0.935493966384356, -0.444790478237349, 
    -0.0888284463372063, 0.793433276899957, -1.37118955226023, 
    -1.27752810419379, 0.571630350274245, 0.38391922015976, -0.585743678190174, 
    -0.639562613892594, 0.637702921021628, 1.02283103079116, 
    0.509051885361466, 0.256796855802238, -0.827467860997893, 
    1.25436407158129, 0.797121499725372, -1.46470541258355, 0.72639012119852, 
    -1.77912640845008, 1.31912635264069, 0.135328148802092, -0.522413009938002, 
    0.680529982119362, 0.068624697834574, -0.598312753345204, 
    0.141370040141094, -0.392378890718311, 1.88269650621348, 
    -3.0968410713246, -0.0622101539722123, -4.1452184094485, 
    -0.954638754603117, -0.106347504757922, -0.716821176235476, 
    0.33910245990621, -1.65370256776216, 0.666505029533247, 1.11178514183042, 
    0.0370564222038934, 0.0466166840013479, -0.557572449898689, 
    -0.961796818639283, 0.936133529770083, -0.283139554139275, 
    -0.111006312537392, 0.655416096433155, 0.253351279215336, 
    -1.27117077274472, 0.821677299062997, 1.30061244464207, -0.571112110007776, 
    -0.978927643078376, -0.0939968112175565, 1.01351341523222, 
    -0.482667556069396, 0.416191169882131, -1.13218300732386, 
    0.0109719515636322, 0.570902411558704, 0.251628490921888, 
    0.757376045856767, -0.286245425992256, -0.850640576775985, 
    0.323694423760568, 0.33667599752107, 0.489882832518856, 0.0192219236731108, 
    -0.267852841112888, 1.81167395220041, -0.0196014744891418, 
    -0.0975879755475657, 1.11193072957353, 1.43135023795345, 
    -0.0901872652728838, 0.562191411596049, 0.0591857591563773, 
    1.10166679368438, -0.140293713526042, 0.0486791770287176, 
    0.34512008662136, 0.818328780971503, -0.238419852381131, 
    -0.368114266866903, 1.03486628422146, 0.539091489689507, 
    -0.233227222876931, -0.351614322647946, -0.108579850152251, 
    1.42892377556831, 0.96726504217144, -0.436055213650844, 0.565831105173759, 
    -1.54960733143962, 1.100259445501, -0.614861226811863, -0.361659876922429, 
    1.40706134947819, -0.552573937385301, 0.105482661464863, 
    -0.374326010572864, -0.0292830594058542, 1.98545718822419, 
    -1.19221368673224, 0.760991474810628, -0.539568099000947, 
    -0.0739542319162944, 0.34373700306183, 0.053071073945822, 
    0.0606901658351647, -0.211219209043705, 0.216590374080456, 
    1.00007081361854, -0.495649129829898, 0.0867746364754286, 
    -1.67723925289802, -0.826836980777755, 1.18863120556783, 
    -0.795681203752549, -0.650869928607352, 0.333545861044237, 
    0.63103014946249, -1.75748236397463, -0.118601139802882, 
    1.51474775013074, 0.132537717059181, -0.677973513449372, 
    0.467947612557183, 1.56786301174147, -0.118528345931329, 
    0.554596584330558, -0.59224659738235, -0.543498968064875, 
    -0.380440695783417, 0.0643541240367275, -0.210830975062082, 
    0.503471021875644, -0.660672836643319, 1.50676468888363, 
    0.780839937121078, -0.116635705270918, -0.240385286913095, 
    0.00044110481212036, 1.4571920623552, -0.350401091455376, 
    0.0850033189342734, 0.197882349091022, 0.726511444317778, 
    -0.331741595713643, 0.837497833814114, 0.609264781867777, 
    0.532151807268005, 0.65446977610295, -0.581909867621652, 
    0.322942220421174, 1.52993740466172, -0.264455793773691, 
    -0.0568476721010507, 1.05299195823846, 0.915435805624833, 
    0.297609953120304, -0.114257772133482, 0.248013061968027, 
    1.64822744593733, 1.26800079018578, -0.0459528559917708, 
    0.720784993088846, -1.05679282101754, 1.38345187047077, -0.64414862780051, 
    -1.25411274217718, 0.177548594303543, -0.257734492966852, 
    -0.818028922319694, 0.409736779937656, -0.216411838547905, 
    1.32536236097051, -0.500938817829506, 0.803770006660658), 
    Tcoded = c(1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 
    1, 2, 2, 3, 3, 3, 2, 3, 3, 2, 3, 3, 2, 3, 2, 2, 2, 2, 3, 
    3, 3, 2, 3, 2, 3, 2, 2, 2, 3, 2, 2, 3, 3, 2, 3, 3, 2, 2, 
    3, 2, 2, 2, 2, 2, 2, 2, 3, 2, 3, 3, 2, 3, 2, 2, 2, 2, 2, 
    2, 2, 2, 2, 2, 2, 2, 3, 3, 2, 2, 2, 2, 3, 2, 2, 2, 2, 4, 
    4, 4, 4, 4, 3, 4, 4, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 
    3, 4, 4, 4, 3, 4, 3, 4, 3, 4, 4, 4, 3, 4, 4, 4, 3, 4, 3, 
    4, 3, 3, 3, 4, 4, 4, 4, 4, 4, 3, 4, 3, 3, 3, 3, 4, 4, 3, 
    3, 3, 3, 3, 3, 3, 4, 3, 3, 3, 3, 4, 3, 3, 3, 3)), row.names = c(NA, 
-222L), class = c("tbl_df", "tbl", "data.frame"))

>Solution :

Try running each individual part of your problem to see what is happening

with(test,
  factor(levels(ID)[1], levels = levels(ID)))

returns

factor(0)
Levels:

so has zero length and ruins everything else (because if any element of expland.grid has length zero the output data.frame has zero rows). You are trying to get the first level of ID before converting it to a factor. Don’t know if you just wanted the first ID? or the ID just as levels instead of as numeric?