Filling option failing when ListLinePlot given my data

Question

Context

I want to do Filled plot such as:

dat1 = {Table[{i^2, i + 1}, {i, 5}], Table[{i^2, i}, {i, 5}]}
ListLinePlot[dat1, PlotStyle -> Red, Filling -> {1 -> {2}}]

But when I apply this to my own data:

dat = 
{
  {{3.0779456558039593`, 3.842486584798708`}, 
   {1.2951669675555262`, 4.05402324780319`}, 
   {0.9196161755899819`, 3.939944632202657`}, 
   {0.5722748507275665`, 3.8875332289711`}, 
   {0.29373287932080444`, 3.7317102841786385`}},
  {{3.0779456558039593`, 7.125115694053534`}, 
   {1.2951669675555262`, 5.8724983311100605`}, 
   {0.9196161755899819`, 5.707473500231869`}, 
   {0.5722748507275665`, 5.114513590881306`}, 
   {0.29373287932080444`, 4.240800591615147`}}
}

It fails to fill the region:

ListLinePlot[dat, PlotStyle -> Red, Filling -> {1 -> {2}}]

Question

Am I missing something obvious?

Answer 1

The cause is your data is out of order. So, the workaround is

ListLinePlot[SortBy[First] /@ dat, PlotStyle -> Red, 
  Filling -> {1 -> {2}}]

I believe it is not a bug. Or, at least, it is an issue that is tangentially discussed in the ListLinePlot documentation. So, while this is certainly disconcerting to see, unusual behavior with unsorted data is expected.