This is my first excursion into using reshape2 and I want to ensure that
the melt() function call is syntactically correct.
The unmodifed data frame is organized this way:
head(tds.anal)
site sampdate param quant
1 UDS-O 2006-12-06 TDS 10800
4 STC-FS 1996-06-14 Cond 280
7 UDS-O 2007-10-04 Mg 1620
9 UDS-O 2007-10-04 SO4 7580
19 JCM-10B 2007-06-21 Ca 79
20 JCM-10B 2007-06-21 Cl 114
What I want looks like this:
site sampdate TDS Cond Mg Ca Cl Na SO4
UDS-O 2006-12-06 10800 NA 1620 NA NA NA 7580
with the actual data for each param, of course.
I've read the reshape.pdf, reshape2.pdf, the ?melt help page, and the
?melt.data.frame help page. I'm still unclear on the differences among
measure.vars, variable.name, and value.name. After several attempts I have
what may be what the melted tds.anal should look like:
m.tds.anal <- melt(tds.anal, id.vars = c('site', 'sampdate', 'param'), \
measure.vars = 'quant', value.name = 'quant', na.rm = F)
> head(m.tds.anal)
site sampdate param variable quant
1 UDS-O 2006-12-06 TDS quant 10800
2 STC-FS 1996-06-14 Cond quant 280
3 UDS-O 2007-10-04 Mg quant 1620
4 UDS-O 2007-10-04 SO4 quant 7580
5 JCM-10B 2007-06-21 Ca quant 79
6 JCM-10B 2007-06-21 Cl quant 114
Is the melt() function call correct? Should the melted result look like
the unmelted ("long" form in Paul Dalgaard's book) data with the additional
'variable' column containing 'quant' for each row?
Rich