time   calls  line
                  1 function [x_power_spec,y_power_spec,h, NFFT]= plot_powerspec(d,data,all,t_start,t_stop, plotOption)
                  2 
                  3 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
                  4 %
                  5 %  function [x_power_spec,y_power_spec,h, NFFT]= plot_powerspec(d,data,all,t_start,t_stop,plotOption)
                  6 % 
                  7 %  Plots a simple power spectrum of requested data
                  8 %
                  9 % Takes sample length by looking at difference between adjacent timestamps
                 10 %  N.B. need to check this as i have found slightly different values
                 11 %  depending on the timestamps selected. Might be better to take length of
                 12 %  data/no. samples
                 13 % 
                 14 % Plots y on log scale and x as linear
                 15 %  h is the handle to the plot
                 16 %
                 17 % Inputs   d: complete data set
                 18 %          data: data you want to plot the power spectrum of
                 19 %           t_start:  start time (in case you only want to plot a subset of the data)
                 20 %           t_stop  : stop_time
                 21 %           all    :  1--> if you want to plot all the data
                 22 %           plotOption:  string of color, etc.
                 23 %               
                 24 %  act 16/6/2010 : Original version
                 25 %  act 3/10/2010 : Changed order of inputs so default is now to plot power
                 26 %                    power spectrum of all the data
                 27 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
                 28 
            66   29 if (all==1) 
            66   30     t_start = 1; 
            66   31     t_stop = length(d.antenna0.receiver.utc); 
            66   32 end; 
                 33 
            66   34 if(nargin<6) 
                 35   plotOption = 'b';
                 36 end
                 37 
                 38 
  0.31      66   39 t_sec = (d.antenna0.receiver.utc(t_start:t_stop)-d.antenna0.receiver.utc(t_start))*24*60*60; 
  0.02      66   40 t_sec = t_sec - t_sec(1); 
            66   41 Fs = 1/(t_sec(3)-t_sec(2)); 
  0.13      66   42 L= length(data(t_start:t_stop)); 
            66   43 NFFT = 2^nextpow2(L); 
  2.84      66   44 y_power_spec = (fft(data(t_start:t_stop),NFFT)/L); 
  0.42      66   45 x_power_spec = Fs/2*linspace(0,1,NFFT/2+1); 
                 46 
                 47 %eval(sprintf('h = semilogy(x_power_spec, 2*abs(y_power_spec(1:NFFT/2+1)),''%s'');', plotOption));
  1.45      66   48 eval(sprintf('h = loglog(x_power_spec, 2*abs(y_power_spec(1:NFFT/2+1)),''%s'');', plotOption)); 
  0.43      66   49 set(gca,'fontsize',5)  
            66   50 return