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Column-reordered table printed when subsetting #3306

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renkun-ken opened this issue Jan 23, 2019 · 4 comments · Fixed by #3352
Closed

Column-reordered table printed when subsetting #3306

renkun-ken opened this issue Jan 23, 2019 · 4 comments · Fixed by #3352
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@renkun-ken
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renkun-ken commented Jan 23, 2019

I notice a strange behavior of print.data.table in latest release. When there's a large number of columns, printing a subsetted data.table will show a column-reordered table, but the result still have correct colnames.

library(data.table)

dt <- data.table(id = 1:10000)
for (i in 1:300) {
  dt[, paste0("v", i) := rnorm(.N)]
}
dt[v100 >= 0]

image

> colnames(dt[v100 >= 0])
  [1] "id"   "v1"   "v2"   "v3"   "v4"   "v5"   "v6"   "v7"   "v8"   "v9"   "v10"  "v11"  "v12"  "v13"  "v14"  "v15"  "v16"  "v17"  "v18"  "v19"  "v20"  "v21"  "v22"  "v23"  "v24" 
 [26] "v25"  "v26"  "v27"  "v28"  "v29"  "v30"  "v31"  "v32"  "v33"  "v34"  "v35"  "v36"  "v37"  "v38"  "v39"  "v40"  "v41"  "v42"  "v43"  "v44"  "v45"  "v46"  "v47"  "v48"  "v49" 
 [51] "v50"  "v51"  "v52"  "v53"  "v54"  "v55"  "v56"  "v57"  "v58"  "v59"  "v60"  "v61"  "v62"  "v63"  "v64"  "v65"  "v66"  "v67"  "v68"  "v69"  "v70"  "v71"  "v72"  "v73"  "v74" 
 [76] "v75"  "v76"  "v77"  "v78"  "v79"  "v80"  "v81"  "v82"  "v83"  "v84"  "v85"  "v86"  "v87"  "v88"  "v89"  "v90"  "v91"  "v92"  "v93"  "v94"  "v95"  "v96"  "v97"  "v98"  "v99" 
[101] "v100" "v101" "v102" "v103" "v104" "v105" "v106" "v107" "v108" "v109" "v110" "v111" "v112" "v113" "v114" "v115" "v116" "v117" "v118" "v119" "v120" "v121" "v122" "v123" "v124"
[126] "v125" "v126" "v127" "v128" "v129" "v130" "v131" "v132" "v133" "v134" "v135" "v136" "v137" "v138" "v139" "v140" "v141" "v142" "v143" "v144" "v145" "v146" "v147" "v148" "v149"
[151] "v150" "v151" "v152" "v153" "v154" "v155" "v156" "v157" "v158" "v159" "v160" "v161" "v162" "v163" "v164" "v165" "v166" "v167" "v168" "v169" "v170" "v171" "v172" "v173" "v174"
[176] "v175" "v176" "v177" "v178" "v179" "v180" "v181" "v182" "v183" "v184" "v185" "v186" "v187" "v188" "v189" "v190" "v191" "v192" "v193" "v194" "v195" "v196" "v197" "v198" "v199"
[201] "v200" "v201" "v202" "v203" "v204" "v205" "v206" "v207" "v208" "v209" "v210" "v211" "v212" "v213" "v214" "v215" "v216" "v217" "v218" "v219" "v220" "v221" "v222" "v223" "v224"
[226] "v225" "v226" "v227" "v228" "v229" "v230" "v231" "v232" "v233" "v234" "v235" "v236" "v237" "v238" "v239" "v240" "v241" "v242" "v243" "v244" "v245" "v246" "v247" "v248" "v249"
[251] "v250" "v251" "v252" "v253" "v254" "v255" "v256" "v257" "v258" "v259" "v260" "v261" "v262" "v263" "v264" "v265" "v266" "v267" "v268" "v269" "v270" "v271" "v272" "v273" "v274"
[276] "v275" "v276" "v277" "v278" "v279" "v280" "v281" "v282" "v283" "v284" "v285" "v286" "v287" "v288" "v289" "v290" "v291" "v292" "v293" "v294" "v295" "v296" "v297" "v298" "v299"
[301] "v300"
@MichaelChirico
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MichaelChirico commented Jan 23, 2019

confirmed incorrect order, though not the same order on my machine\

@MichaelChirico
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MichaelChirico commented Jan 23, 2019

Root is rbind reordering columns:

dt[v100 >= 0, colnames(rbind(head(.SD, 5), tail(.SD, 5)))]
  [1] "id"   "v226" "v225" "v1"   "v2"   "v227" "v228" "v3"   "v4"   "v229" "v230" "v5"   "v6"   "v231" "v232" "v7"   "v8"   "v233"
 [19] "v234" "v9"   "v10"  "v235" "v236" "v11"  "v12"  "v237" "v238" "v13"  "v14"  "v239" "v240" "v15"  "v16"  "v241" "v242" "v17" 
 [37] "v18"  "v243" "v244" "v19"  "v20"  "v245" "v246" "v21"  "v22"  "v247" "v248" "v23"  "v24"  "v249" "v250" "v25"  "v26"  "v251"
 [55] "v252" "v27"  "v28"  "v253" "v254" "v29"  "v30"  "v255" "v256" "v31"  "v32"  "v257" "v258" "v33"  "v34"  "v259" "v260" "v35" 
 [73] "v36"  "v261" "v262" "v37"  "v38"  "v263" "v264" "v39"  "v40"  "v265" "v266" "v41"  "v42"  "v267" "v268" "v43"  "v44"  "v269"
 [91] "v270" "v45"  "v46"  "v271" "v272" "v47"  "v48"  "v273" "v274" "v49"  "v50"  "v275" "v276" "v51"  "v52"  "v277" "v278" "v53" 
[109] "v54"  "v279" "v280" "v55"  "v56"  "v281" "v282" "v57"  "v58"  "v283" "v284" "v59"  "v60"  "v285" "v286" "v61"  "v62"  "v287"
[127] "v288" "v63"  "v64"  "v289" "v290" "v65"  "v66"  "v291" "v292" "v67"  "v68"  "v293" "v294" "v69"  "v70"  "v295" "v296" "v71" 
[145] "v72"  "v297" "v298" "v73"  "v74"  "v299" "v300" "v75"  "v76"  "v150" "v149" "v151" "v152" "v77"  "v78"  "v153" "v154" "v79" 
[163] "v80"  "v155" "v156" "v81"  "v82"  "v157" "v158" "v83"  "v84"  "v159" "v160" "v85"  "v86"  "v161" "v162" "v87"  "v88"  "v163"
[181] "v164" "v89"  "v90"  "v165" "v166" "v91"  "v92"  "v167" "v168" "v93"  "v94"  "v169" "v170" "v95"  "v96"  "v171" "v172" "v97" 
[199] "v98"  "v173" "v174" "v99"  "v100" "v175" "v176" "v101" "v102" "v177" "v178" "v103" "v104" "v179" "v180" "v105" "v106" "v181"
[217] "v182" "v107" "v108" "v183" "v184" "v109" "v110" "v185" "v186" "v111" "v112" "v187" "v188" "v113" "v114" "v189" "v190" "v115"
[235] "v116" "v191" "v192" "v117" "v118" "v193" "v194" "v119" "v120" "v195" "v196" "v121" "v122" "v197" "v198" "v123" "v124" "v199"
[253] "v200" "v125" "v126" "v201" "v202" "v127" "v128" "v203" "v204" "v129" "v130" "v205" "v206" "v131" "v132" "v207" "v208" "v133"
[271] "v134" "v209" "v210" "v135" "v136" "v211" "v212" "v137" "v138" "v213" "v214" "v139" "v140" "v215" "v216" "v141" "v142" "v217"
[289] "v218" "v143" "v144" "v219" "v220" "v145" "v146" "v221" "v222" "v147" "v148" "v223" "v224"

Can be fixed by setting use.names = FALSE but I'm not sure this is intended behavior of rbind to begin with...

@MichaelChirico
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MichaelChirico commented Jan 23, 2019

Funnily enough rbind works perfectly for smaller # of columns; only kicks in for wider tables (probably why this hasn't come up before):

ncol = 30
DT = setDT(replicate(ncol, rnorm(3L), simplify = FALSE))
identical(colnames(rbind(DT[1], DT[3])), colnames(DT))
# [1] TRUE


ncol = 300
DT = setDT(replicate(ncol, rnorm(3L), simplify = FALSE))
identical(colnames(rbind(DT[1], DT[3])), colnames(DT))
# [1] FALSE

@DrKodiak
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DrKodiak commented Feb 1, 2019

I was about to file a separate bug report when I came across this post.
rbind rearranges columns when there are more than 254 columns. This only happens with data.tables, not data.frames. Setting use.names to FALSE prevents this.


library(data.table)

a <- data.table(t(1:254))
b <- rbind(a,a)
all(colnames(b) == colnames(a))
# TRUE

a <- data.table(t(1:255))
b <- rbind(a,a)
all(colnames(b) == colnames(a))
# FALSE

a <- data.frame(t(1:255))
b <- rbind(a,a)
all(colnames(b) == colnames(a))
# TRUE

a <- data.table(t(1:255))
b <- rbind(a,a, use.names = F)
all(colnames(b) == colnames(a))
# TRUE

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