Using a vector of indexes to acces a multidimensional vector

First i want to say that i'm pretty new with matlab but i'm quite experienced in other programming leanguages.

So I have a structure called n_gram buit with a variable number of cells each containing a n dimension array. If for exemple n=2 i will have a 20x20 array and so on.

i also have a variable that hold the indexes i need to acess on the n dimension array tempInd=cell(1,n) each cell has an array with L elements. In this problem i need to make L acesses into the n-dim array. And the indexes of the cell i need to acess can be found from tempInd like so seq=(tempInd{1}(i),tempInd{2}(i),......,tempInd{n},(i)) with 1<=i<=L. So like this i will have L sequences of n indexes that specify where in the multydim array i should add put L values in tempVal.

The problem is that even if i create the array seq with n elements indicating the indexes for each dimension they are all treated like single linear indexes. So doing

n_gram{p}(seq)=n_gram{p}(seq)+ tempVal(i)

just adds the tempVal(i) to the n linear interpeted indexes

% p here is the idex of the object in consideration, be awere that each element has it's own multydim array all with the same size
%tempInd and tempVal are respectivly a n cell array holding a 1,L array each and a 1,L array holding an integer for each position
dim=[];
    for i=1:n
        dim(i)=20;  %this is going to be the dimension vector i use to generate my multydim array
    end
    n_gram{p}=zeros(dim); %This will be my Multydimensional Array , it will always be a 20x20x ...x20 n times
    
    for i=1:L
        seq=zeros(1,n); %this is the vector i want to use to access the multydim Array...
        for j=1:n  %here i do the cicle that extracts the n coordinates i need to index a specific position in the array.
            seq(j)=tempInd{j}(i); 
        end
        %HERE THE PROBLEM
        n_gram{p}(seq)=n_gram{p}(seq)+ tempVal(L); %indexing into the matrix by using the 1,n size seq array doesn't work
    end
    

I thought the best way is to convert the n indexes into linear indexing but the fact that i don't know the value of the n until the funcion is called breaks me.

[vlad iosif]

I just wrote this function that convert my n-sequence of indexes into a linear index. This method only works for squared array.

function [outputArg1] = linInd(indexes,n)
temp=indexes(1);
for i=2:length(indexes)
        temp=temp + (n^(i-1)*(indexes(i)-1));
end
outputArg1=temp;
end

Answer 1

[Bruno Luong]

Check out this thread I provide three ways to convert nd-indexes to linear index.