[Rd] truncation/rounding bug with write.csv

Dirk Eddelbuettel
Wed, 14 Mar 2018 12:53:54 -0000

What OS are you on?  On Ubuntu 17.10 with R 3.4.3 all seems well (see
below for your example, I just added a setwd()).

[ That said, I long held a (apparently minority) view that csv is for all
intends and purposes a less-than-ideal format.  If you have that much data,
you do generally not want to serialize it back and forth as that is slow, and
may drop precision.  The rds format is great for R alone; we now have C code
to read it from other apps (in the librdata repo by Evan Miller).  Different
portable serializations work too (protocol buffer, msgpack, ...), there are
databases and on and on... ]

Dirk


R> df <- data.frame(replicate(100, runif(1000000, 0,1)))
R> setwd("/tmp")
R> write.csv(df, "temp.csv")
R> system('tail -n1 temp.csv')
"1000000",0.11496100993827,0.740764639340341,0.519190795486793,0.736045523779467,0.537115448853001,0.769496953347698,0.102257401449606,0.437617724528536,0.173321532085538,0.351960731903091,0.397348914295435,0.496789071243256,0.463006566744298,0.573105450021103,0.575196429155767,0.821617329493165,0.112913676071912,0.187580146361142,0.121353451395407,0.576333721866831,0.00763232703320682,0.468676633667201,0.451408475637436,0.0172415724955499,0.946199159137905,0.439950440311804,0.109224532730877,0.657066411571577,0.0524766123853624,0.54859598656185,0.94473168021068,0.500153199071065,0.636756601976231,0.221365773351863,0.620196332456544,0.559639401268214,0.198483835440129,0.397874651942402,0.710652963491157,0.317212327616289,0.239299293374643,0.0606942125596106,0.165786643279716,0.667431530542672,0.436631754040718,0.812185280025005,0.374252707697451,0.421187321422622,0.730321826180443,0.904493971262127,0.399387824581936,0.650714065413922,0.594219180056825,0.147960299625993,0.941945064114407,0.357223904458806,0.275038427906111,0.191008436959237,0.957893384154886,0.211530723143369,0.680650093592703,0.503884038887918,0.754094189498574,0.74776051659137,0.673691919771954,0.236221367260441,0.825558929471299,0.21071959589608,0.246618688805029,0.686810691142455,0.0247942050918937,0.572868114337325,0.494058627169579,0.684360746992752,0.0139967589639127,0.626861660508439,0.417218193877488,0.410173830809072,0.390906651504338,0.477168896235526,0.382211019750684,0.597674581920728,0.198329919017851,0.0684413285925984,0.450342149706557,0.133007253985852,0.755873151356354,0.372862737858668,0.762442974606529,0.582133987685665,0.692048883531243,0.259269661735743,0.147847984684631,0.635266482364386,0.320955650880933,0.00151186063885689,0.446474697208032,0.0673662247136235,0.791947861900553,0.0973296447191387
R> system('head -n2 temp.csv')
"","X1","X2","X3","X4","X5","X6","X7","X8","X9","X10","X11","X12","X13","X14","X15","X16","X17","X18","X19","X20","X21","X22","X23","X24","X25","X26","X27","X28","X29","X30","X31","X32","X33","X34","X35","X36","X37","X38","X39","X40","X41","X42","X43","X44","X45","X46","X47","X48","X49","X50","X51","X52","X53","X54","X55","X56","X57","X58","X59","X60","X61","X62","X63","X64","X65","X66","X67","X68","X69","X70","X71","X72","X73","X74","X75","X76","X77","X78","X79","X80","X81","X82","X83","X84","X85","X86","X87","X88","X89","X90","X91","X92","X93","X94","X95","X96","X97","X98","X99","X100"
"1",0.995067856274545,0.0237177284434438,0.839840568602085,0.99880409357138,0.455015312181786,0.967688028467819,0.191194181796163,0.903533136472106,0.570170691236854,0.86230118968524,0.23530788696371,0.30707904486917,0.256274404237047,0.369592409580946,0.989929250674322,0.50812312704511,0.806819133926183,0.536566868191585,0.0863138805143535,0.294523851014674,0.676951135974377,0.195627561537549,0.261776751372963,0.383222601376474,0.578275503357872,0.79082652577199,0.19860127940774,0.0204593606758863,0.659964868798852,0.42379029514268,0.69516694964841,0.0594558380544186,0.124592808773741,0.289328144863248,0.524508266709745,0.84306427766569,0.317027662880719,0.273440480465069,0.111866136547178,0.217484838794917,0.354757327819243,0.973936082562432,0.673076402861625,0.300948366522789,0.219195493729785,0.912278874544427,0.276768424082547,0.959344451315701,0.500720858341083,0.431024399353191,0.814444699790329,0.0738761406391859,0.600137831410393,0.639816240407526,0.405302967177704,0.941259450744838,0.190415472723544,0.0382565588224679,0.486769351176918,0.127647049957886,0.558708024444059,0.686994878342375,0.176803215174004,0.794697789475322,0.59406904829666,0.0897431457415223,0.196549082174897,0.0750515828840435,0.736311340238899,0.00494878669269383,0.383522965712473,0.960385771468282,0.101023471681401,0.209177070530131,0.798869548132643,0.147874428424984,0.187238642480224,0.148522146046162,0.32379064662382,0.620601811446249,0.201180462958291,0.179565666476265,0.466121524339542,0.245493365218863,0.980698639061302,0.342919659335166,0.387780519668013,0.393966492731124,0.148554262006655,0.521724705817178,0.722740866011009,0.105151653522626,0.461909410310909,0.905382365221158,0.0736293855588883,0.636923864483833,0.540197744267061,0.425208077067509,0.666353516280651,0.584139186656103
R>

--
http://dirk.eddelbuettel.com | @eddelbuettel | edd at debian.org