Document how to use add.elem for read.msc

[mwtoews]

The documentation doesn't say how to use add.elem for read.msc. It is used to identify and read other attributes from the MSC archive file format.

The add.elem list or data.frame structure must have 5 fields:

• alias : a number code used in the file
• name : a short name, no spaces or non-ASCII characters
• long.name : a longer name for axis labels
• units : units for axis labels
• scale : a multiplier to transform the archive data to meaningful numbers that match the units

The built-in elements (internally as elem.all) are:

   alias      name                  long.name units scale
1      1     t_max  daily maximum temperature    °C 0.100
2      2     t_min  daily minimum temperature    °C 0.100
3      3    t_mean     daily mean temperature    °C 0.100
4     10      rain             total rainfall    mm 0.100
5     11      snow             total snowfall    mm 0.100
6     12    precip        total precipitation    mm 0.100
7     13    snow_d          snow on the groud    cm 1.000
8     77     press           station pressure   kPa 0.010
9    123      rain            hourly rainfall    mm 0.100
10   133       sun                   sunshine   hrs 0.100
11    61     solar RF1 global solar radiation MJ/m² 0.001
12    64 net_solar RF4 net-all wave radiation MJ/m² 0.001

So to add one custom element:

dat <- read.msc(fname, add.elem=list(alias=123, name="my_var", long.name="My variable",
                                     units="mm", scale=0.1))

and multiple elements can be added by constructing a data.frame that can be combined with the internal elem.all structure with rbind. The internal elem.all can be expanded on request.

The task is to complete the built-in documentation for R.