1st draft R code to access met data in Clowder + geostreams

[dlebauer]

Submitting draft for feedback, please don't merge until useable

• @max-zilla please review the clowder API section. I would like to download a netCDF file using the API but not sure how
• @Zodiase could you review and add content, e.g. from github discussions?

[max-zilla]

@dlebauer I made some edits to the file, but I didn't want to merge to your branch blindly so I created my own:
https://github.com/terraref/tutorials/blob/geostreams_met_max/sensors/01-meteorological-data.Rmd

Aside from cleaning up some comments...

• will automatically download ALL .nc files in the Sample Data directory to specified local directory using for loop (~150 MB total)
• will aggregate measure (e.g. solar spectrum) across all .nc files for time plot

Note that I had to coerce the time into as.numeric because my R skills are rusty and the ymd format was creating weird Y/M/D/h/m/s matrices I couldn't properly concatenate - I thought you might see an easy way to cast that as user-friendly YMD for plotting.

This is the key snippet for downloading:

print(paste0("Downloading ", sources[i], " to ", outputs[i]))
  f <- CFILE(outputs[i], mode = "wb")
  curlPerform(url = sources[i], writedata = f@ref)
  RCurl::close(f)