I have a data.frame, which I can plot using matplot:

> dim(lhbyzone)
[1] 38070    21
> matplot(lhbyzone)
(no error occurs here)

But if I take the head of lh, and try, it gives me a strange error:

> foo <- head(lhbyzone,1000)
> matplot(foo)
Error in `rownames<-`(`*tmp*`, value = c("1", "2", "3", "4", "5", "6",  : 
  length of 'dimnames' [1] not equal to array extent

So, maybe something to do with the names? 

> dimnames(foo)
[[1]]
   [1] "1"    "2"    "3"    "4"    "5"    "6"    "7"    "8"    "9"    "10"  
  [11] "11"   "12"   "13"   "14"   "15"   "16"   "17"   "18"   "19"   "20"  
  [21] "21"   "22"   "23"   "24"   "25"   "26"   "27"   "28"   "29"   "30"  
  [31] "31"   "32"   "33"   "34"   "35"   "36"   "37"   "38"   "39"   "40"  
...
 [951] "951"  "952"  "953"  "954"  "955"  "956"  "957"  "958"  "959"  "960" 
 [961] "961"  "962"  "963"  "964"  "965"  "966"  "967"  "968"  "969"  "970" 
 [971] "971"  "972"  "973"  "974"  "975"  "976"  "977"  "978"  "979"  "980" 
 [981] "981"  "982"  "983"  "984"  "985"  "986"  "987"  "988"  "989"  "990" 
 [991] "991"  "992"  "993"  "994"  "995"  "996"  "997"  "998"  "999"  "1000"

[[2]]
 [1] "time" "z1"   "z2"   "z3"   "z4"   "z5"   "z6"   "z7"   "z8"   "z9"  
[11] "z10"  "z11"  "z12"  "z13"  "z14"  "z15"  "z16"  "z17"  "z18"  "z19" 
[21] "z20" 

> dim(foo)
[1] 1000   21

> names(foo)
 [1] "time" "1"    "2"    "3"    "4"    "5"    "6"    "7"    "8"    "9"   
[11] "10"   "11"   "12"   "13"   "14"   "15"   "16"   "17"   "18"   "19"  
[21] "20"

The dimensions look the same? It's odd, since matplot on the original frame works, but not on the head of the frame. What could be happening here?

Edit, ok, so to answer some questions, and let's use thbyzone instead of lhbyzone, because it's smaller, and let's use head instead of head(..,1000) to make the data smaller

> head(thbyzone)
r
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