[R] Descriptive Stats from Data Frame

[Rich Shepard]

On Wed, 31 Aug 2011, Tal Galili wrote:

> It is a bit hard to read the "summary" you are using.  Consider please
> pasting the output of:
> ls.str(chemdata)

Tal,

   Yes, summary() is inappropriate. I do want str() instead. And what that
shows is:

> str(chemdata)
'data.frame':   14886 obs. of  1 variable:
  $ site_id.sample_date.param.quant: Factor w/ 14886 levels
"BC-0.5|1996-04-19|Arsenic|0.01",..: 11579 14219 13298 11982 11909 13371
13082 111 12 23 ...

> Regarding your question, please start and see if this work (I'm not sure,
> since it seems you have made some changes to the summary output, and I am
> only guessing how things look):

> mean(chemdata$quant[chemdata$param > =="Arsenic"])

> mean(chemdata$quant[chemdata$param > =="Arsenic"])
Error: unexpected '==' in "mean(chemdata$quant[chemdata$param > =="
> mean(chemdata$quant[chemdata$param =="Arsenic"])
[1] NA
Warning message:
In mean.default(chemdata$quant[chemdata$param == "Arsenic"]) :
   argument is not numeric or logical: returning NA

   I find it easy following the syntax in the half-dozen or more books I've
read, but quite difficult to apply what I read to my own real-world data.
:-)

Thanks,

Rich