Decimal numbers in a triple for loop

2 ビュー (過去 30 日間)
Auryn_
Auryn_ 2018 年 3 月 21 日
コメント済み: Auryn_ 2018 年 3 月 22 日
Hi all, I want to run the equation for a range of q variables at an increment such as
q = 0.1:0.1:1;
I need to use a for loop, where actually I include 2 additional for loops:
a & b are 2 cells.
M=10;
for i=1:length(q)
for i1=1:M
for i2=1:M
n_pm(i)=n_pm(i)+exp(-1i*q(i)*(i1-i2))*a{i1}*b{i2};
end
end
n_pmT(i)=n_pm(i)/(2*M)^2;
end
This code however gives me either the error 'Subscript indices must either be real positive integers or logicals' or 'Index exceeds matrix dimensions', depending on how I define q in the loop.
Looking forward for some help!
Thank you in advance.
  1 件のコメント
James Tursa
James Tursa 2018 年 3 月 21 日
It would help if you copy & pasted the entire error message for us, including the offending line.

サインインしてコメントする。

回答 (2 件)

James Tursa
James Tursa 2018 年 3 月 21 日
Have you inadvertently created a variable with the name 'exp' in your workspace? If so, clear it and don't use that name for a variable.
  4 件のコメント
Auryn_
Auryn_ 2018 年 3 月 22 日
Hi,
the error 'Index exceeds matrix dimensions' appears even if I use:
q = 0.1:0.1:1;
for i=1:length(q)
for i1=1:M
for i2=1:M
n_pm(i)=n_pm(i)+q(i)*(i1-i2)*a{i1}*b{i2};
end
end
n_pmT(i)=n_pm(i)/(2*M)^2;
end
James Tursa
James Tursa 2018 年 3 月 22 日
This error:
'Subscript indices must either be real positive integers or logicals' or 'Index exceeds matrix dimensions'
was probably caused by a variable named 'exp' in your workspace.
This error:
'Index exceeds matrix dimensions'
is different, and means exactly what it says. Did you use the dbstop debugging tip I gave you? When the code paused, what were these values:
i
i1
i2
numel(q)
numel(n_pm)
numel(n_pmT)
numel(a)
numel(b)

サインインしてコメントする。


Auryn_
Auryn_ 2018 年 3 月 22 日
編集済み: Auryn_ 2018 年 3 月 22 日
Hi,
now it seems to work!
M=10;
q = 0.1:0.1:1;
n_pmT=zeros(length(q),1);
n_pm=zeros(M,M,length(q));
for i=1:length(q)
for i1=1:M
for i2=1:M
n_pm=n_pm+exp(-1i*q(i)*(i1-i2))*a{i1}*b{i2};
end
end
n_pmT(i)=n_pm(i)/(2*M)^2;
end
  2 件のコメント
James Tursa
James Tursa 2018 年 3 月 22 日
Well, it may run but I have my doubts that this code actually does what you want it to. Inside your inner loop you have n_pm=n_pm+etc. Do you realize that the etc part is added to all of the elements of n_pm at each iteration? Is that what you really want?
Auryn_
Auryn_ 2018 年 3 月 22 日
Hi James, I want a sum over the indices i1 and i2. Is that correct in the code? Thanks again!

サインインしてコメントする。

カテゴリ

Help Center および File ExchangeLoops and Conditional Statements についてさらに検索

Community Treasure Hunt

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

Start Hunting!

Translated by