rmarkdown to html: tables do not render if + or - present in header row

[oliverdrechsel]

As soon as one puts strings ending with '+' or '-' in the header of tables, they will not render as table, but as normal text, in html.

The issue was described with example data here:
http://stackoverflow.com/questions/35798605/how-to-markdown-html-tables-containing-plus-minus

[jgm]

Example from linked post:

|               | IP_gene8-_1st| IP_gene8+_1st| 
|:--------------|-------------:|-------------:|
|IP_gene8-_1st  |     1.0000000|     0.4357325|
|IP_gene8+_1st  |     0.4357325|     1.0000000|

[jgm]

Minimal cases:

| a-_b |
|------|
| 1    |

| a+_b |
|----|
|  1|

[jgm]

Interestingly revealing case:

pandoc -t native
| a |
|----| 
| a+_b |
| 1 |
^D
[Table [] [AlignDefault] [0.0]
 [[Plain [Str "a"]]]
 [[[Plain [Str "a+_b",Space,Str "|",SoftBreak,Str "|",Space,Str "1",Space,Str "|"]]]]]

[jgm]

Workaround until the bug is fixed: escape the _ characters as \_.

[jgm]

Note also that pandoc allows + as well as | as a pipe separator. (This is to achieve compatibility with org-mode tables, which are easy to create in Emacs.)

So literal + characters should be backslash-escaped.

[oliverdrechsel]

I tried a bit more and it seems the \_ is necessary to get a valid html table.

a+_b doesn't work
a\+_b doesn't work
a+\_b works
a+b works