PROCEDURE: CONV3D conv3d, tvar3d, $ selparam_idx=selparam_idx, $ selparam_dat=selparam_dat, $ newname=newname PURPOSE: Convert 3D data to 2D or 1D data KEYWORDS: tvar3d: tplot variables for 3D data selparam_idx: a vector with 3 elements to identify the loaded variables when converting 3D data to 2D or 1D data. selparam_dat: a vector with 3 elements to identify the coordinate. when converting 3D data to 2D or 1D data. newname: if set, then name of the converted data will be newname. This keyword is available only when selparam_idx is set. EXAMPLE: conv3d, 'kyushugcm_T', selparam_idx=[0,0,1], selparam_dat=[30., 50., 0] loads 1D data along z-axis at (x,y)=(30.,50.). conv3d, 'kyushugcm_T', selparam_idx=[1,1,0], selparam_dat=[0., 0., 100.] loads 2D data on the x-y plane at z=100. Written by Y.-M. Tanaka, Dec.24, 2012 (ytanaka at nipr.ac.jp)