CODEWITHSUNDEEP
c++matlab
user3275596
user3275596

Reputation: 31

MATLAB equivalent in c++

In MATLAB inorder to access the odd or even rows and columns of a matrix we use 

A = M(1:2:end,1:2:end);

Is there an equivalent for this in C++? or How do i do this in C++.

Basically what i want to do is in matlab i have

A(1:2:end,1:2:end) = B(1:2:end,:);
A(2:2:end,2:2:end) = B(2:2:end,:);

I want to implement the same in C++

Upvotes: 2

Views: 873

Answers (3)

gire
gire

Reputation: 1105

In C++ the for loop is constructed as follows

for (initial state; condition for termination; increment)

So if you are looking for the odd elements, you can:

for (int i = 0; i < size; i += 2),

whereas if you are looking for the even elements:

for (int i = 1; i < size; i += 2).

Where size depends if you are looping through the rows or columns. Take into account that because C++ arrays start at index 0, your odd elements will correspond to even indexes and your even elements will correspond to odd indexes.

Now, the answer: If you want to get the elements of a matrix, in C++ you must loop through the matrix with a for loop. You can modify the elements you access by modifying the increment property of the for loop.

Upvotes: 0

lakshmen
lakshmen

Reputation: 29094

for(int i= 0; i < rows/2; i++)
  for(int j= 0; j < columns/2; j++)
    A[i][j] = M[i*2][j*2];

Upvotes: 0

MSalters
MSalters

Reputation: 180145

This is available only in a fairly obscure class, std::valarray. You need a std::gslice (Generalized slice) with stride {2,2} to access the std::valarray.

Upvotes: 2

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