Is this the correct syntax for replacing a specific element in a dependent vector?

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Real Name
Real Name on 27 Dec 2016
Commented: Real Name on 28 Dec 2016
numElem = 9990;
w = linspace(2*pi,2*pi*10^18,numElem);
wRes = 2*pi*10^9;
for n = 1:numElem
if w(n) > wRes
w = [w(1:n), wRes, w(n:numElem)];
end
end
freq = w ./ (2*pi);
lambda = 299792458 ./ freq;
if w == wRes
B = 2*pi./lambda;
else
B = pi/2 .*w./wRes;
end
I am trying to create a range of w's and make sure that a specific value, wRes is in there. For that specific wRes, I want an exceptional value for B. Is the above code the correct way of going about it?

Accepted Answer

Walter Roberson
Walter Roberson on 27 Dec 2016
Note that if you are trying to replace values > wRes with wRes, then another way of doing that is:
w = min(w, wRes);
  1 Comment
Real Name
Real Name on 28 Dec 2016
I figured it out, my code was really bad. I had meant to insert wRes into a sorted vector and keep the order.

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More Answers (1)

Brendan Hamm
Brendan Hamm on 27 Dec 2016
It looks like you are trying to change any values of w which are greater than wRes to be wRes instead, but you are instead placing an additional element into w at the (n+1)th position and then at the next iteration checking if that value is greater than wRes. I think what you are looking for is logical indexing.
idx = w > wRes;
The ith index of idx is true (1) if w(i) > wRes. Now you can use this to access the elements of w where idx is true and change only those values:
w(idx) = wRes;
Consider this on a simpler example:
x = 1:10;
idx = x > 5; % 6th through 10th elements are true!
x(idx) = -1; % 6th through 10th elements are now -1!

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