function atom = import_pdb_traj(filename,varargin)
fileID = fopen(filename,'r');
Line1 = {fgets(fileID)};
Line2 = {fgets(fileID)};
nAtoms=str2double(Line1);
Box_cell=strsplit(char(Line2));
LineEnd = textscan(fileID, '%s',inf);
fclose(fileID);

idx = strfind(char(Box_cell(1)),'#');
Box_dim=[];
if numel(idx) >0
    for i=1:length(Box_cell);
        [num, status] = str2num(char(Box_cell(i)));
        j=1;
        if status==1;
            Box_dim=[Box_dim num];
            j=j+1;
        end
    end
end

Boxinfo='maybe';
if nargin>1;
    Frames=[1:varargin{1}];
    if nargin>2;
        Frames=[1:varargin{2}:max(Frames)];
    end
else
    if numel(Box_dim)==0
        Frames=1:(size(LineEnd{1,1},1)+1)/(4*nAtoms);
        Boxinfo='no';
    else
        Frames=1:(size(LineEnd{1,1},1)+1)/(4*nAtoms);
    end
end

traj=zeros(length(Frames),nAtoms*3);
Box_dim=zeros(length(Frames),3);
fileID = fopen(filename,'r');

if strcmp(Boxinfo,'no')
    for t=1:length(Frames)

        frewind(fileID)
        startRow = 1+nAtoms*(Frames(t)-1)+2*(Frames(t)-1);

        Line1 = {fgets(fileID)};
        Line2 = {fgets(fileID)};
        nAtoms=str2double(Line1);
        %         Box_cell=strsplit(char(Line2));

        formatSpec = '%s%f%f%f%[^\n\r]';
        dataArray = textscan(fileID, formatSpec, nAtoms, 'Delimiter',{'\t',' '}, 'MultipleDelimsAsOne', true, 'EmptyValue' ,NaN,'HeaderLines',0, 'ReturnOnError', false);

        traj(t,1:3:end)=[dataArray{:,2}];
        traj(t,2:3:end)=[dataArray{:,3}];
        traj(t,3:3:end)=[dataArray{:,4}];

        if t==1;
            XYZ_labels = dataArray{:,1};
            XYZ_data = [dataArray{:,2} dataArray{:,3} dataArray{:,4}];
        end

        Box_dim(t,:) = [(max([dataArray{:,2}])-min([dataArray{:,2}]))*1.001    (max([dataArray{:,3}])-min([dataArray{:,3}]))*1.001  (max([dataArray{:,4}])-min([dataArray{:,4}]))*1.001];

        if mod(t,10)==0;
            t
        end
    end
    disp('Guessing the box dimensions to be .1% larger than the max-min distances')
else
    for t=1:length(Frames)

        frewind(fileID)
        startRow = 1+nAtoms*(Frames(t)-1)+2*(Frames(t)-1);

        Line1 = {fgets(fileID)};
        Line2 = {fgets(fileID)};
        nAtoms=str2double(Line1);
        Box_cell=strsplit(char(Line2));

        idx = strfind(char(Box_cell(1)),'#');
        Box_dim=[];
        if numel(idx) >0
            for i=1:length(Box_cell);
                [num, status] = str2num(char(Box_cell(i)));
                j=1;
                if status==1;
                    Box_dim=[Box_dim num];
                    j=j+1;
                end
            end
        end

        formatSpec = '%s%f%f%f%[^\n\r]';
        dataArray = textscan(fileID, formatSpec, nAtoms, 'Delimiter',{'\t',' '}, 'MultipleDelimsAsOne', true, 'EmptyValue' ,NaN,'HeaderLines',0, 'ReturnOnError', false);

        traj(t,1:3:end)=[dataArray{:,2}];
        traj(t,2:3:end)=[dataArray{:,3}];
        traj(t,3:3:end)=[dataArray{:,4}];

        if t==1;
            XYZ_labels = dataArray{:,1};
            XYZ_data = [dataArray{:,2} dataArray{:,3} dataArray{:,4}];
        end

        if mod(t,10)==0;
            t
        end

    end
end
fclose(fileID);

for i=1:nAtoms;
    atom(i).resname={'MOL'};
    atom(i).molid=1;
    atom(i).type    = XYZ_labels(i,1);
    atom(i).fftype  = XYZ_labels(i,1);
    atom(i).charge      = 0;
    atom(i).index=mod(i,100000);
    atom(i).neigh.type  = {};
    atom(i).neigh.index  = zeros(6,1);
    atom(i).neigh.dist  = zeros(6,1);
    atom(i).bond.type  = zeros(6,1);
    atom(i).bond.index  = zeros(6,1);
    atom(i).angle.type  = zeros(6,1);
    atom(i).angle.index  = zeros(6,1);
    atom(i).x = XYZ_data(i,1);
    atom(i).y = XYZ_data(i,2);
    atom(i).z = XYZ_data(i,3);
    atom(i).vx=0;
    atom(i).vy=0;
    atom(i).vz=0;
end

atom = resname_atom(atom);

assignin('caller','atom',atom);
assignin('caller','traj',traj);
assignin('caller','nAtoms',nAtoms);
assignin('caller','Box_dim',Box_dim);
assignin('caller','XYZ_labels',XYZ_labels);
assignin('caller','XYZ_data',XYZ_data);


if Frames(end) == size(traj,1)
    sprintf('.xyz traj file imported %d frames', Frames(end))
else
    sprintf('Number of frames is wrong somehow')
end