If statement in a loop

2017 5 9
1 个回答
更新时间：2017 5 10
14 次查看（30 天）

0 个投票

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 个评论
显示 -1更早的评论 隐藏 -1更早的评论

Jan
Jan 2017-5-9
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?

请先登录，再进行评论。

请先登录，再回答此问题。

回答（1 个）

Jan
Jan 2017-5-9
编辑：Jan 2017-5-9

0 个投票

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 个评论
显示 3更早的评论 隐藏 3更早的评论

sedef kocakaplan
sedef kocakaplan 2017-5-9
Hi Jan,
Thank you for your answer. Sorry for not giving detail explanation. F_l is a vector. (F_l = zeros(length(reale),1). I want F_l (at the else part), change in values as co increases. Yet matlab calculates the all the F_l values only with co=co(end).
Jan
Jan 2017-5-9
In your original code you overwrite the elements of F_l in each iteration of the for c loop. What do you want to obtain instead? Currently all we see is the failing assignment of the elements of this array. But what do you want instead? "change in values as co increases" is clear, but at which index should which value appear?
sedef kocakaplan
sedef kocakaplan 2017-5-9
For co 2,3,4... F_l(ni=9,12,15...) should be written.
Also pre-definition of F_l is,
F_l = zeros(length(reale),1);
sedef kocakaplan
sedef kocakaplan 2017-5-9
Dear Jan,
I re-write the code in a different way. Thanks for your comments.
Jan
Jan 2017-5-10
@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.

请先登录，再进行评论。

类别

在 帮助中心 和 File Exchange 中查找有关 Loops and Conditional Statements 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by