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  1. MATLAB: Adjusting the dynamic range of a plot of logarithmic values
  2. %% Constants
  3. fnum = 1;
  4. Fc = 1/16;
  5. taup = 128;
  6. taumin = 1;
  7. taumax = 512;
  8. taux = taumin:taumax;
  9.  
  10. %% Signal
  11. l = 1:16; %Signal length
  12. s = sin(2*pi*Fc*l); %Original Signal
  13. sig = zeros([1 taup+512]);
  14. sig(taup:taup+size(l,2)-1) = s;
  15.  
  16. [mfr,fdy] = MatchedFilterResponse(sig,taup,l);
  17. Z = mfr;
  18.  
  19. slices = true;
  20. %full dynamic range
  21. name = 'Short Tone Ping results with 0dB range';
  22. Zmag = abs(Z).^2;
  23. Zn = normalizeMat(Zmag);
  24. Zdb = 10*log10(1+Zn);
  25. fnum = plotSurfaces(taux,fdy,Zdb,fnum,name,slices);
  26.  
  27. slices = false;
  28. %40dB dynamic range
  29. name = 'Short Tone Ping results with 40dB range';
  30. Z40mag = Zmag;
  31. Z40n = normalizeMat(Z40mag);
  32. Z40n(Z40n<0.0001) = 0.0001;
  33. Z40db = 10*log10(1+Z40n);
  34. fnum = plotSurfaces(taux,fdy,Z40db,fnum,name,slices);
  35.  
  36. function [mfr,fdy] = MatchedFilterResponse(sig,taup,l)
  37.     Fdmin = -1/16;
  38.     Fdmax = 1/16;
  39.     Fdinc = (0.125)/(255);
  40.     fdy = linspace(Fdmin,Fdmax,256);
  41.     i = 0;
  42.     for tau = 1:512
  43.         i = i+1;
  44.         j = 0;
  45.         for Fd = Fdmin:Fdinc:Fdmax
  46.             j = j+1;
  47.             a = sig(l+taup-1);
  48.             b = sig(l+tau).*exp(1i*2*pi*Fd*l);
  49.             mfr(j,i) = sum(a.*b);
  50.         end
  51.     end
  52. return
  53. end
  54.  
  55. function [fnum] = plotSurfaces(taux,fdy,z,fnum,name,slices)
  56.     fid = figure(fnum);
  57.     axes1 = axes('Parent',fid);
  58.     grid(axes1,'on');
  59.     hold(axes1,'all');
  60.     msh = mesh(taux,fdy,z,'Parent',axes1);
  61.     xlabel ('Delay - seconds');
  62.     ylabel ('Frequency offset from center frequency - Cycles/sample');
  63.     zlabel ('Ambiguity function (Normalized Magnitude-Squared)','Visible','off');
  64.     fname = strcat(name,' (Ambiguity Function z(tau;F_d))');
  65.     title(fname);
  66.     ax = axis;
  67.     axis([50 200 ax(3) ax(4)])
  68.     cb = colorbar('peer',axes1);
  69.     set(get(cb,'ylabel'),'String','Magnitude-Squared (dB)');
  70.     hold off;
  71.     fnum = fnum + 1;
  72.     return
  73. end
  74.        
  75. data = 10 .^ randn(100,100);                      % large dynamic range data
  76. ncols = 128;                                      % number of colors in the colormap
  77. R1 = [linspace(0,1, 10)'; ones(ncols - 10, 1); ]; % colormap for the small values
  78. R2 = [zeros(ncols - 10, 1); linspace(0,1,10)'];   % colormap for the large values
  79. G = zeros(ncols, 1);
  80. B = zeros(ncols, 1);
  81. cmap1 = [R1, G, B];
  82. cmap2 = [R2, G, B];
  83.  
  84. figure
  85. subplot(1,2,1)
  86. rgbplot(cmap1) % plot the colormap values
  87. subplot(1,2,2)
  88. imagesc (data) % plot the data
  89. colormap(cmap1)
  90. colorbar
  91.  
  92. figure
  93. subplot(1,2,1)
  94. rgbplot(cmap2)
  95. subplot(1,2,2)
  96. imagesc (data)
  97. colormap(cmap2)
  98. colorbar
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