Can't understand this MATLAB syntax?

Question

for i=0:255
m(i+1)=sum((0:i)'.*p(1:i+1)); end

Someone can explain what is happening. p is a 256 element array equal to m.

+3

matlab

siddharth 09 Apr 12 at 8:35

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2 answers

Regardless p

, you can calculate m

with:

dm = (0 : length(p) - 1)' .* p(:); % process as column vector
m = cumsum(dm);

Hint: write the formula for m [n], then for m [n + 1], then subtract to get the formula:

m[n+1] - m[n] = (n - 1) * p[n]

and this dm

.

+1

Serg 09 Apr 12 at 14:03

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0x90 · Accepted Answer · 2012-04-09T08:41:08+0000

p = (0:255)';
m = zeros(1,256);
for i=0:255
    m(i+1)=sum((0:i)'.*p(1:i+1)); 

end

m[i+1]

contains a dot product [0,1,2,..,i]

with(p[1],...,p[i+1])

You can write it like:

p = (0:255);
m = zeros(1,256);
for i=0:255
    m(i+1)=sum((0:i).*p(1:i+1)); 

end

Or:

p = (0:255);
m = zeros(1,256);
for i=0:255
    m(i+1)=(0:i)*p(1:i+1)'; 

end

If you don't remember, this is the definition of a scalar product