MATLAB: Plotting sequences over intervals

signal processing

Hello,

How would I go about plotting a seqeunce over the below intervals?

A) ?(?) = 2?(? + 1)− ?(? −6), −10 ≤ ? ≤ 10.

B) ?(?) = {… , 5, 4, 3, 2, 1, 5, 4, 3, 2, 1, 5, 4, 3, 2, 1, … }; −20 ≤ ? ≤ 12.

Thanks

Best Answer

You could do it like this

n = -10:10
x = zeros(length(n),1) % preallocate array of zeros to hold result
for k = 1:length(n)
    % evaluate x(n)
    x(k) = 2*usmpl(n(k)+ 1) - usmpl(n(k)-6);
end
% plot result
stem(n,x)
% define helper function
function delta = usmpl(n)
% define unit sample function
if n == 1
    delta = 1
else
    delta = 0
end
end

Related Solutions

MATLAB: Plotting a Sequence over a Given Interval

I have no idea.

I would just do something like this, and hope for the best with respect to whatever that exp() call is supposed to do:

u = @(t) t>=1;
x = @(n) n.*(u(n)-u(n-10) + 10*exp(-0*(n-10)) .* (u(n-10)-u(n-20)));
n = linspace(0, 20, 1000);
figure
plot(n, x(n))
grid

Make appropriate changes when you resolve the problem with the exponential term.

MATLAB: A function that computes the sum of a geometric series.

cumprod is a great idea. Well done for thinking of it.

You state that your function did not execute. This may be because it does not have a function header. All you have written is a script.

Have you confused n and N? The code you wrote assumes n.

So how did you call it? What error do you get? Show the full text of the error.

You've made a good start in what you did, so some variations that should work:

function S = geosum1(r,n)
  S = sum(cumprod([1,r*ones(1,n)]));
function S = geosum2(r,n)
  S = sum(cumprod([1,repmat(r,1,n)]));

It can also be done without cumprod.

function S = geosum3(r,n)
  S = sum(r.^(0:n));

Of course, you can break it into multiple lines. That makes the code more readable, and MATLAB does not charge extra if you use an extra line. For example:

 function S = geosum4(r,n)
   % sum of a geometric series, up to r^n, as
   %   1 + r + r^2 + ... + r^n
   % Note there will be n+1 terms in the series.
   % generate a vector to be then prodded together
   v = [1,r*ones(1,n)];
   % use cumprod, instead of using exponents
   % to compute each term as r^k
   p = cumprod(v);
   % sum the terms
   S = sum(p);

Comments are very important, as they help you to understand what you wrote, when you are forced to debug code written a year ago (or 30 years ago.) As well, too often once finds code written by a colleague, that you need to use. It can be crucial to be able to understand and follow their code if you will then use it and trust it.

Any of the above schemes will work. To verify that fact, we can even do this:

geosum3(sym('r'),3)
ans =
r^3 + r^2 + r + 1

Best Answer

Related Solutions

MATLAB: Plotting a Sequence over a Given Interval

MATLAB: A function that computes the sum of a geometric series.

Related Question