discrete-time real exponential signal

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cikalekli
cikalekli on 23 Nov 2021
Answered: Paul on 24 Nov 2021
HOW CAN I DELETE THOSE POINTS WHICH ARE VISIBLE AT ZERO AT COUPLE TIMES?
I was trying to create a power signal as with α = -0.9 between -10 < t < 10
Here is the graph which I was trying to achieve:
clc; clear; close all
alpha = -.9;
t = -10 : 0.5 : 10;
y = power(alpha, t);
stem(t,y, '- b',...
'LineWidth',2);
Warning: Using only the real component of complex data.
title ('\bf\it 3rd QUESTION ', 'fontsize', (25));
xlabel ('\bf INPUT ', 'fontsize', (20));
ylabel ('\bf OUTPUT ', 'fontsize', (20));

Accepted Answer

Paul
Paul on 24 Nov 2021
Those points at zero show up because alpha is negative and the code is raising alpha to non-integer powers t. For those values of t, alpha^t is complex, and they all have real part equal 0 for those values of t. For example
alpha = -.9;
power(alpha,-9.5)
ans = 0.0000 + 2.7208i
Then, as the warning states, stem() plots the real part, which is why those zero points show up.
The solution is to only define t with integer values
t = -10 : 1 : 10;
y = power(alpha, t);
stem(t,y, '- b','LineWidth',2);

More Answers (2)

VBBV
VBBV on 23 Nov 2021
Edited: VBBV on 23 Nov 2021
clc; clear; close all
alpha = -.9;
t = -10 : 0.10000 : 10;
y = exp(alpha.^t); % exponent of alpha is vector t
stem(t,real(y));
xlabel('xlabel')
ylabel('Magnitude')
  1 Comment
VBBV
VBBV on 23 Nov 2021
clc; clear; close all
alpha = -.9;
t = -10 : 0.50000 : 10;
y = (alpha.^t); % exponent of alpha is vector t
stem(t(3:2:end),real(y(3:2:end)),'linewidth',2,'MarkerFaceColor','blue');
xlabel('xlabel')
ylabel('Magnitude')
Do you mean like figure above ? where the first two points are not visible

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cikalekli
cikalekli on 23 Nov 2021
The expected result and your code is a lot different as you can see.
Here I made it more accurate version:
clc; clear; close all
alpha = -.9;
t = -10 : 0.5 : 10;
y = power(alpha, t);
stem(t,y, '- b',...
'LineWidth',2);
Warning: Using only the real component of complex data.
title ('\bf\it 3rd QUESTION ', 'fontsize', (25));
xlabel ('\bf INPUT ', 'fontsize', (20));
ylabel ('\bf OUTPUT ', 'fontsize', (20));
  1 Comment
cikalekli
cikalekli on 23 Nov 2021
How can I delete those points which are visible at zero
They are visible at couple times as you can see?

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