plotprob.m

《Fundamentals of Statistical Signal Processing》（《随机信号处理基础》）的配套MATLAB源代码。为电信工程师、教师、和学生而设计。

%  plotprob.m
%
   function plotprob(x,Qx,xlab,ylab,nor)
%  This program plots a set of right-tail probabilities 
%  (complementary cumulative distribution function) on normal
%  probability paper.
%
%  Input Parameters:
%
%    x    - Real column vector of x values for desired 
%           right-tail probabilities
%    Qx   - Real column vector of corresponding 
%           right-tail probabilities
%    xlab - Label for x axis (enclose in single quotes)
%    ylab - Label for y axis (enclose in single quotes)
%    nor -  Set equal to 1 for Gaussian right-tail probability
%           to be plotted for comparison, and 0 otherwise
%
%  Verification Test Case:
%
%  The inputs x=[-5:0.01:5]';Qx=0.5*Q(x)+0.5*Q(x/sqrt(2));xlab='x';
%  ylab='Right-tail Probability';nor=1; should produce Figure 2.4.
%
%  Set up y-axis values.
   y=[0.0001 0.001 0.01 0.1 0.3 0.5 0.7 0.9 0.99 0.999 0.9999]';
%  Set up x-axis limits.
   xmax=Qinv(min(y));
%  Warp y values for plotting.
   m=(2*min(y)-1)/(2*xmax);
   Y=m*Qinv(Qx)+0.5;
%  Check to see if Q(x) (Gaussian right-tail probability)
%  is to be plotted.
   if nor==1
     xnor=[-xmax:0.01:xmax]';
     ynor=m*xnor+0.5;
     plot(x,Y,'-',xnor,ynor,'--')
   else
     plot(x,Y)
   end
   xlabel(xlab)
   ylabel(ylab)
   axis([-xmax xmax min(y) max(y)]);
%  Determine y tick mark locations by warping.
   Ytick=m*Qinv(y)+0.5;
%  Set up y axis labels.
   t=['0.0001';' 0.001';'  0.01';'   0.1';'   0.3';'   0.5';...
      '   0.7';'   0.9';'  0.99';' 0.999';'0.9999'];
   set(gca,'Ytick',Ytick)
   set(gca,'Yticklabels',t)
   grid