Rule to handling the symbol
e.g. http://www.data.jma.go.jp/obd/stats/data/mdrr/man/remark.html
Types
- Zero...
--
- No recorded a value (missing)... ,
×
,///
,空白
,#
- Less than a value...
0
(> 1),0.0
,0+
,10-
- Observational Error
- Remark ...
)
,]
,*
Should enhancement convert_error()
.