function [ne,mlatsrc,mlonsrc,xg,v1,Ti,Te,J1,v2,v3,J2,J3,filename,Phitop,ns,vs1,Ts] = loadframe(direc,ymd,UTsec,flagoutput,mloc,xg)

cwd = fileparts(mfilename('fullpath'));

addpath([cwd, '/../script_utils'])

narginchk(3,6)

validateattr(direc, {'char'}, {'vector'}, mfilename, 'data directory', 1)

validateattr(ymd, {'numeric'}, {'vector', 'numel', 3}, mfilename, 'year month day', 2)

validateattr(UTsec, {'numeric'}, {'vector'}, mfilename, 'UTC second', 3)

if nargin < 5 || isempty(flagoutput) || isempty(mloc)

[~,~,~,~,flagoutput,mloc] = readconfig([direc, filesep, 'inputs']);

end

validateattr(flagoutput,{'numeric'},{'scalar'},mfilename,'output flag',4)

if ~isempty(mloc)

validateattr(mloc, {'numeric'}, {'vector', 'numel', 2}, mfilename, 'magnetic coordinates', 5)

end

if nargin < 6 || isempty(xg)

xg = readgrid([direc, '/inputs']);

end

validateattr(xg, {'struct'}, {'scalar'}, mfilename, 'grid structure', 6)

direc = absolute_path(direc);

%% SET MAGNETIC LATITUDE AND LONGITUDE OF THE SOURCE

if nargout >= 2 && ~isempty(mloc)

mlatsrc=mloc(1);

mlonsrc=mloc(2);

else

mlatsrc=[];

mlonsrc=[];

end

%% LOAD DIST. FILE

stem0 = datelab(ymd, UTsec);

for ext = {'.h5', '.dat'}

stem = stem0;

filename = [stem, ext{1}];

if is_file([direc, filesep, filename])

break

end

% switch microsecond to one for first time step

stem(end) = '1';

filename = [stem, ext{1}];

if is_file([direc, filesep, filename])

break

end

end

assert(is_file([direc, filesep, filename]), ['loadframe: ', [direc,filesep,stem,'.{dat,h5}'], ' does not exist.'])

switch flagoutput

case 1

[ne,v1,Ti,Te,J1,v2,v3,J2,J3,ns,vs1,Ts,Phitop] = loadframe3Dcurv(direc,filename);

case 2

[ne,v1,Ti,Te,J1,v2,v3,J2,J3,Phitop] = loadframe3Dcurvavg(direc,filename);

ns=[]; vs1=[]; Ts=[];

otherwise

ne=loadframe3Dcurvne(direc,filename);

v1=[]; Ti=[]; Te=[]; J1=[]; v2=[]; v3=[]; J2=[]; J3=[];

ns=[]; vs1=[]; Ts=[]; Phitop=[];

end

end % function