Index: trunk/src/transform_field/signal_FFT.m
===================================================================
--- trunk/src/transform_field/signal_FFT.m	(revision 677)
+++ trunk/src/transform_field/signal_FFT.m	(revision 677)
@@ -0,0 +1,67 @@
+% 'FFT': calculate and display spectrum of the field selected in the GUI  get_field 
+%  GUI_input=FFT(hget_field)
+%
+% OUTPUT: 
+% GUI_input: option for display in the GUI get_field
+%
+%INPUT:
+% hget_field: handles of the GUI get_field
+%
+
+function DataOut=signal_FFT(DataIn)
+% global spec x_vec
+% %requests for the visibility of input windows in the GUI series  (activated directly by the selection in the menu ACTION)
+% if ~exist('hget_field','var')
+%     GUI_input={'check_1Dplot'};
+%     return %exit the function 
+% end
+% GUI_input=[];
+% %initiation
+% hhget_field=guidata(hget_field);
+% abscissa_list=get(hhget_field.abscissa,'String');
+% val=get(hhget_field.abscissa,'Value');
+% val=val(1);
+% abscissa_name=abscissa_list{val};
+% ordinate_list=get(hhget_field.ordinate,'String');
+% val=get(hhget_field.ordinate,'Value');
+% val=val(1); %take only the first variable in the list
+DataOut=DataIn;
+ordinate_name=DataIn.ListVarName{2};
+abscissa_name=DataIn.ListVarName{1};
+
+% get variable
+Var= DataIn.(ordinate_name);
+Coord_x= DataIn.(abscissa_name);
+np=size(Var);
+np_freq=floor(np(1)/2);
+dx=1;%default
+dfreq=1/np(1);%default frequency interval (abscissa= array index)
+sum_data=sum(Var,2);
+
+ind_select=find(~isinf(Coord_x)&~isnan(sum_data));%detect infinite values
+Coord_x=Coord_x(ind_select);
+Var=Var(ind_select,:);
+diff_x=diff(Coord_x);
+dx=min(diff_x);
+%interpolate on a regular abscissa interval if needed
+if (max(diff_x)-dx)> 0.001*dx || numel(ind_select)<np(1)
+    xequ=Coord_x(1):dx:Coord_x(end);%equal time spacingdx=
+    Var=interp1(Coord_x,Var,xequ); %interpolated func
+    np=size(Var);
+end
+%   funcinterp=interp1(time,func,timeq); %interpolated func
+dfreq=1/(Coord_x(end)-Coord_x(1));%frequency interval
+freq_max=1/(2*dx);
+Var=Var-ones(np(1),1)*mean(Var,1); %substract mean value
+fourier=fft(Var);%take fft (complex)
+spec=abs(fourier).*abs(fourier);% take square of the modulus
+spec=spec(1:np_freq,:);%keep only the first half (the other is symmetric)
+
+%plot
+figure(2);
+x_vec=linspace(dfreq,freq_max,np_freq);
+plot(x_vec',spec)
+xlabel('frequency (Hz)')
+ylabel('spectral intensity')
+grid on
+