For loop for the variable and plot

Hello,

I have a matrix of correlations between particles (50 particles). I want to compute the correlations between them, at a distance l. That is, I need to compute V_a,V_(a+l).

If my variable V(a,a,b) where

a=1:50
b=1:100

Now I would like to make a loop and plot the following:

sum_a(V(a,a+l,:))

May I ask you to help me with this loop and the plot?

I have tried with this:

M=50;

   for a=1:M
       for l=a:M
          V(a,l,:)=sum(V(a,a+l,:));
       end
   end

Unfortunately it doesn't work.

Thanks in advance for your reply.

[Jan]

I do not understand the question. What exactly is "V_a,V_(a+l)"?

Does "sum_a(V(a,a+l,:))" mean:

M = V(1:50, (1:50)+l, :)
sum(M(:))

? What is "l" here? If the 2nd dimension has a length of a, a+l exceeds the array dimensions.

By the way: Do not use "l" (lowercase L) as a name, because it is hard to distinguish from 1.

[Walter Roberson]

Duplicates https://www.mathworks.com/matlabcentral/answers/379186-loop-and-plot-in-2d

[Auryn_]

Hi,

I want

M=\sum_{a}[V(a, a+k,:)]

That is, a sum only in one of the variables.

With k I want to say that I want the interaction V(1,1+k,:) for a=1, etc.

k will go from 0 to 50.

I do not know how to express a and k in the for loop to express the correlations in the whole matrix.

[Jan]

@Auryn_: I could try to make a smart guess, what "M=\sum_{a}[V(a, a+k,:)]" might mean. But why do you use a magic notation instead of a syntax the readers can know already? I do not understand the description as text also: "a sum only in one of the variables".

I still do not understand, what you are asking for. "I want the interaction V(1,1+k,:) for a=1, etc." How could I know what "etc." means here? What should be continued how? a=2, or V(2, 1+k, :), or V(1, 2+k, :), or b=1? Please explain it again. Maybe the mathematical notation helps.

While this thread has been closed, explain it clearly in the other thread: https://www.mathworks.com/matlabcentral/answers/379186-loop-and-plot-in-2d.