1  %'proj_grid': project fields with unstructured coordinantes on a regular grid


2  % 


3  % function [A,rangx,rangy]=proj_grid(vec_X,vec_Y,vec_A,rgx_in,rgy_in,npxy_in)


4 


5 


6  function [A,rangx,rangy]=proj_grid(vec_X,vec_Y,vec_A,rgx_in,rgy_in,npxy_in)


7  if length(vec_Y)<2


8  msgbox_uvmat('ERROR','less than 2 points in proj_grid.m');


9  return;


10  end


11  diffy=diff(vec_Y); %difference dy=vec_Y(i+1)vec_Y(i)


12  index=find(diffy);% find the indices of vec_Y after wich a change of horizontal line occurs(diffy non zero)


13  if isempty(index); msgbox_uvmat('ERROR','points aligned along abscissa in proj_grid.m'); return; end;%points aligned% A FAIRE: switch to line plot.


14  diff2=diff(diffy(index));% diff2 = fluctuations of the detected vertical grid mesh dy


15  if max(abs(diff2))>0.001*abs(diffy(index(1))) % if max(diff2) is larger than 1/1000 of the first mesh dy


16  % the data are not regularly spaced and must be interpolated on a regular grid


17  if exist('rgx_in','var') & ~isempty (rgx_in) & isnumeric(rgx_in) & length(rgx_in)==2% positions imposed from input


18  rangx=rgx_in; % first and last positions


19  rangy=rgy_in;


20  % npxy=npxy_in;


21  dxy(1)=1/(npxy_in(1)1);%grid mesh in y


22  dxy(2)=1/(npxy_in(2)1);%grid mesh in x


23  dxy(1)=(rangy(2)rangy(1))/(npxy_in(1)1);%grid mesh in y


24  dxy(2)=(rangx(2)rangx(1))/(npxy_in(2)1);%grid mesh in x


25  else % interpolation grid automatically determined


26  rangx(1)=min(vec_X);


27  rangx(2)=max(vec_X);


28  rangy(2)=min(vec_Y);


29  rangy(1)=max(vec_Y);


30  dxymod=sqrt((rangx(2)rangx(1))*(rangy(1)rangy(2))/length(vec_X));


31  dxy=[dxymod/4 dxymod/4];% increase the resolution 4 times


32  end


33  xi=[rangx(1):dxy(2):rangx(2)];


34  yi=[rangy(1):dxy(1):rangy(2)];


35  [XI,YI]=meshgrid(xi,yi);% creates the matrix of regular coordinates


36  A=griddata_uvmat(vec_X,vec_Y,vec_A,xi,yi');


37  A=reshape(A,length(yi),length(xi));


38  else


39  x=vec_X(1:index(1));% the set of abscissa (obtained on the first line)


40  indexend=index(end);% last vector index of line change


41  ymax=vec_Y(indexend+1);% y coordinate AFTER line change


42  ymin=vec_Y(index(1));


43  %y=[vec_Y(index) ymax]; % the set of y ordinates including the last one


44  y=vec_Y(index);


45  y(length(y)+1)=ymax;


46  nx=length(x); %number of grid points in x


47  ny=length(y); % number of grid points in y


48  B=(reshape(vec_A,nx,ny))'; %vec_A reshaped as a rectangular matrix


49  [X,Y]=meshgrid(x,y);% positions X and Y also reshaped as matrix


50 


51  %linear interpolation to improve the image resolution and/or adjust


52  %to prescribed positions


53  test_interp=1;


54  if exist('rgx_in','var') & ~isempty (rgx_in) & isnumeric(rgx_in) & length(rgx_in)==2% positions imposed from input


55  rangx=rgx_in; % first and last positions


56  rangy=rgy_in;


57  npxy=npxy_in;


58  else


59  rangx=[vec_X(1) vec_X(nx)];% first and last position found for x


60  % rangy=[ymin ymax];


61  rangy=[max(ymax,ymin) min(ymax,ymin)];


62  if max(nx,ny) <= 64 & isequal(npxy_in,'np>256')


63  npxy=[8*ny 8*nx];% increase the resolution 8 times


64  elseif max(nx,ny) <= 128 & isequal(npxy_in,'np>256')


65  npxy=[4*ny 4*nx];% increase the resolution 4 times


66  elseif max(nx,ny) <= 256 & isequal(npxy_in,'np>256')


67  npxy=[2*ny 2*nx];% increase the resolution 2 times


68  else


69  npxy=[ny nx];


70  test_interp=0; % no interpolation done


71  end


72  end


73  if test_interp==1%if we interpolate


74  xi=[rangx(1):(rangx(2)rangx(1))/(npxy(2)1):rangx(2)];


75  yi=[rangy(1):(rangy(2)rangy(1))/(npxy(1)1):rangy(2)];


76  [XI,YI]=meshgrid(xi,yi);


77  A = interp2(X,Y,B,XI,YI);


78  else %no interpolation for a resolution higher than 256


79  A=B;


80  XI=X;


81  YI=Y;


82  end


83  end 
