If statement in a loop

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sedef kocakaplan
sedef kocakaplan il 9 Mag 2017
Commentato: Jan il 10 Mag 2017
Hi everyone,
I am trying to run the code below. The problem is co is not working in a loop. I just obtained the last raw for the computation. What should I do to work the code with a looping co?(F_l is a force vector)
co = 1;
for c = 1:na-2
co=co+1
for ni = 3:3:length((reale))
if ni==3;
F_l(ni) = 2*pi*((DeltaR/na)/6);
elseif ni==6;
F_l(ni) =2*pi*( ((DeltaR/na)/3)+ (2/na+2/na)*DeltaR/6);
elseif ni==length((reale));
F_l(ni)=2*pi*((na-1)/na+2)*DeltaR/6;
else
F_l(ni) =2*pi*( ((DeltaR*((co-1)/na+2*co/na))/6)+ ((DeltaR*((co+1)/na+2*co/na))/6)) ;
end
end
end
  1 Commento
Jan
Jan il 9 Mag 2017
The question is not clear. Of course you can use co inside a loop and inside the if branches. Please explain what "co is not working" exactly means. What does "the last row for the computation" mean?

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Risposte (1)

Jan
Jan il 9 Mag 2017
Modificato: Jan il 9 Mag 2017
With some guessing:
co = 1;
F_l = zeros(length(reale), na - 2); % Pre-allocate!!!
for c = 1:na-2
co = co + 1;
for ni = 3:3:length(reale)
if ni == 3
F_l(ni, c) = 2*pi*((DeltaR/na)/6);
elseif ni == 6
F_l(ni, c) = 2*pi*(((DeltaR/na)/3) + (2/na+2/na)*DeltaR/6);
elseif ni == length(reale)
F_l(ni, c) = 2*pi*((na-1)/na+2)*DeltaR/6;
else
F_l(ni, c) = 2*pi*(((DeltaR*((co-1)/na+2*co/na))/6) + ...
((DeltaR*((co+1)/na+2*co/na))/6));
end
end
end
Is this the wanted result? Should F_l contain the zeros for ni=1,2, etc.? Then the code can be simplified:
co = 1;
nr = length(reale);
F_l = zeros(nr, na - 2); % Pre-allocate!!!
F_l(3, 1:na-2) = 2*pi*((DeltaR/na)/6);
F_l(6, 1:na-2) = 2*pi*(((DeltaR/na)/3) + (2/na+2/na)*DeltaR/6);
F_l(nr, 1:na-2) = 2*pi*((na-1)/na+2)*DeltaR/6;
for c = 1:na-2
co = co + 1;
F_l(9:3:length(reale)-3, c) = 2*pi*(((DeltaR*((co-1)/na+2*co/na))/6) + ...
((DeltaR*((co+1)/na+2*co/na))/6));
end
And even this can be written without a loop.
  5 Commenti
sedef kocakaplan
sedef kocakaplan il 9 Mag 2017
Dear Jan,
I re-write the code in a different way. Thanks for your comments.
Jan
Jan il 10 Mag 2017
@sedef kocakaplan: This is not clear: "For co 2,3,4... F_l(ni=9,12,15...) should be written." These are 2 loop counters: one for co and one for ni. But you get one vector as output only.

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