discrete-time real exponential signal

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));

Answer 1

[Paul]

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);

Answer 2

[cikalekli]

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));

[cikalekli]

How can I delete those points which are visible at zero

They are visible at couple times as you can see?