MATLAB: Help in performing a summation

summation

I need to perform the following summation for k that goes from i to N (i goes from 0 to N): p_i= ∑ w_k/((1-pi)^(k-i+1))

Best Answer

w is expected to be a [1 x N] vector.

p = zeros(1, N);
for  k = 1:N
  p(k) = sum(w(k:N) ./ ((1 - piH) .^ (1:N-k+1)));
end

[EDITED], or if w is a column vector:

p = zeros(1, N);
for  k = 1:N
  p(k) = sum(w(k:N).' ./ ((1 - piH) .^ (1:N-k+1)));
end

Related Solutions

MATLAB: *** Write a function called triangle_wave that computes the sum (−1) sin(2 +1) (2 +1) for each of 1001 values of t uniformly spaced from 0 to 4π inclusive. The input argument is a scalar non-negative integer n, and the output argument is a row v

denominator = (2 * k + 1) .^ 2;

Use the elemtnwise .^ instead of the matrix operation ^ . The same for "(-1)^k" .

The corresponding error message is clear:

 Error using  ^ 
 Inputs must be a scalar and a square matrix.
 To compute elementwise POWER, use POWER (.^) instead.

[EDITED] The formula contains: "Sum from k=0 to n", you code contains:

k = 1:n;

Replace this by k = 0:n. It will be more efficient to move the definition before the loop and pre-allocate the output:

function S = triangle_wave(n)                                      
t = linspace(0, 4*pi, 1001);
S = zeros(size(t));   % Pre-allocation
k = 0:n;              % Not 1:n
for tIndex = 1 : length(t) 
  numerator   = ((-1) .^ k) .* sin(t(tIndex) .* (2 * k + 1));
  denominator = (2 .* k + 1) .^ 2;
  S(tIndex)   = sum(numerator ./ denominator);
end

MATLAB: Problem with using lsim which lead to row and column error

Hello Raymond, your system has two inputs, therefore w needs to be a 2-by-n array, rather than a 1-by-n. Use instead:

 ...
 t = 0:0.01:10; 
 w = zeros(2, length(t)); 
 k = 1;
 for n = 1:length(t) 
    if k < 100 
        w(:,k) = 0; 
    elseif k >= 100&&k <= 301; 
        w(:,k) = 1; 
    else w(:,k) = 0; 
    end
    k = k+1; 
 end
 y = lsim(clsys, w, t); 
 plot (t, y);

...and adapt to your needs as necessary.

Best Answer

Related Solutions

MATLAB: *** Write a function called triangle_wave that computes the sum (−1) sin(2 +1) (2 +1) for each of 1001 values of t uniformly spaced from 0 to 4π inclusive. The input argument is a scalar non-negative integer n, and the output argument is a row v

MATLAB: Problem with using lsim which lead to row and column error

Related Question