graph shifting and for loops problem

Question

Charles Moody 2018-2-25

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/384670-graph-shifting-and-for-loops-problem

编辑： Walter Roberson 2018-3-22

I have 2 questions:

1) In this code I use a for loop to populate a linespace that U must graph. But because logicals must be non zero, non negative I always have to start at element 1. But I have to plot it when element 1 in the linespace has to be at the o position on the graph.

2) I have nested loops that indicate the phase angle of a function. This is based off of the sign of the real and imaginary parts of the function. For some reason the phase as shown on the graph is wrong.

%constants
A =1;
B = .5;
j = sqrt(-1);
f1 = 1000; %Hz
f2 = 3000; %Hz
fs = 8000; %Hz
phi = .75*pi;
N1 = 8;
%time linespace
t = 0:1/fs:((N1-1)/fs);
g1 = sin(2*f1*pi*t)+B*sin(2*f2*pi*t + phi);
%for an 8-point DFT we need 12 input samples
xn1 = zeros(1,8);
for i = 1:8
    xn1(i) = g1(i);
end
MN1_Matrix = zeros(8,8);
for i = 1:8
      for k = 1:8
          MN1_Matrix(i,k) = xn1(k)*(cos((((k-1)*2*pi*(i-1))/N1))-(j*sin(((k-1)*2*pi*(i-1))/N1)));
      end
  end
disp(MN1_Matrix)
for i = 1:8
    X1_0(i) = cumsum(MN1_Matrix(1,i));
    X1_1(i) = cumsum(MN1_Matrix(2,i));
    X1_2(i) = cumsum(MN1_Matrix(3,i));
    X1_3(i) = cumsum(MN1_Matrix(4,i));
    X1_4(i) = cumsum(MN1_Matrix(5,i));
    X1_5(i) = cumsum(MN1_Matrix(6,i));
    X1_6(i) = cumsum(MN1_Matrix(7,i));
    X1_7(i) = cumsum(MN1_Matrix(8,i));
end
X1_R = [sum(real(X1_0)) sum(real(X1_1)) sum(real(X1_2)) sum(real(X1_3)) sum(real(X1_4)) sum(real(X1_5)) sum(real(X1_6)) sum(real(X1_7))];
X1_I = [sum(imag(X1_0)) sum(imag(X1_1)) sum(imag(X1_2)) sum(imag(X1_3)) sum(imag(X1_4)) sum(imag(X1_5)) sum(imag(X1_6)) sum(imag(X1_7))]; 
for i = 1:8
X1_MAG(i) = sqrt((X1_R(i)^2) + (X1_I(i)^2));
end
for i = 1:8
    if X1_I(i) == 0
        X1_ANGLE = 0;
    elseif X1_R(i) == 0 && X1_I(i) > 0
        X1_ANGLE = -90;
    elseif X1_R(i) == 0 && X1_I(i) < 0
        X1_ANGLE = 90;
    else
        X1_ANGLE(i) = atand(X1_I(i)/X1_R(i));
    end
end
subplot(2,2,1)
stem(X1_MAG)
xlabel('bin (m*1 kHz)')
ylabel('magnitude')
title('Magnitude of X(m)')
axis([0 9 0 4])
subplot(2,2,2)
stem(X1_ANGLE)
xlabel('bin (m*1 kHz)')
ylabel('phase')
title('Degree Phase of X(m)')
axis([0 9 -100 100])
subplot(2,2,3)
stem(X1_R)
xlabel('bin (m*1 kHz)')
ylabel('magnitude')
title('Real Part of X(m)')
axis([0 9 -.5 1.5])
subplot(2,2,4)
stem(X1_I)
xlabel('bin (m*1 kHz)')
ylabel('magnitude')
title('Imag Part of X(m)')
axis([0 9 -4 4])