FUNCTION get_sd_ave :Description: Obtain a tplot variable-type structure storing a time series of the values averaged over the given latitude/longitude range. :PARAMTERS: vn : a tplot variable the values in which are to be averaged :KEYWORD: latrng: the geographical latitude range for which the given values are averaged lonrng: the geographical longitude range for averaging maglat: Set this keyword if you give the latrng in magnetic latitude new_vn: Set a string to create a new tplot variable containing the averaged values :EXAMPLES: erg_load_sdfit, site='hok',/get dat = get_sd_ave( 'sd_hok_vlos_1', latrng=[60,70], lonrng=[140,170] :Author: Tomo Hori (E-mail: horit@stelab.nagoya-u.ac.jp) :HISTORY: 2011/07/03: Created $LastChangedBy: jwl $ $LastChangedDate: 2014-02-10 16:54:11 -0800 (Mon, 10 Feb 2014) $ $LastChangedRevision: 14265 $ $URL: svn+ssh://thmsvn@ambrosia.ssl.berkeley.edu/repos/spdsoft/trunk/projects/erg/ground/radar/superdarn/get_sd_ave.pro $