As the title says. Is there a way to iterate through array in .txt file without using any for loops? To be more clear, I need to check if elements of that array belongs to interval without using any for loops at all, but I can't find how to do it, all solutions on the internet has for loops.
Iteration Without the Implementation of Loops
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arrays - How do I iterate through each element in an n-dimensional matrix in MATLAB? - Stack Overflow
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You can use linear indexing to access each element.
for idx = 1:numel(array)
element = array(idx)
....
end
This is useful if you don't need to know what i,j,k, you are at. However, if you don't need to know what index you are at, you are probably better off using arrayfun()
The idea of a linear index for arrays in matlab is an important one. An array in MATLAB is really just a vector of elements, strung out in memory. MATLAB allows you to use either a row and column index, or a single linear index. For example,
A = magic(3)
A =
8 1 6
3 5 7
4 9 2
A(2,3)
ans =
7
A(8)
ans =
7
We can see the order the elements are stored in memory by unrolling the array into a vector.
A(:)
ans =
8
3
4
1
5
9
6
7
2
As you can see, the 8th element is the number 7. In fact, the function find returns its results as a linear index.
find(A>6)
ans =
1
6
8
The result is, we can access each element in turn of a general n-d array using a single loop. For example, if we wanted to square the elements of A (yes, I know there are better ways to do this), one might do this:
B = zeros(size(A));
for i = 1:numel(A)
B(i) = A(i).^2;
end
B
B =
64 1 36
9 25 49
16 81 4
There are many circumstances where the linear index is more useful. Conversion between the linear index and two (or higher) dimensional subscripts is accomplished with the sub2ind and ind2sub functions.
The linear index applies in general to any array in matlab. So you can use it on structures, cell arrays, etc. The only problem with the linear index is when they get too large. MATLAB uses a 32 bit integer to store these indexes. So if your array has more then a total of 2^32 elements in it, the linear index will fail. It is really only an issue if you use sparse matrices often, when occasionally this will cause a problem. (Though I don't use a 64 bit MATLAB release, I believe that problem has been resolved for those lucky individuals who do.)
I have 3 matrices(4x4) (M0T1, M1T2, M2T3) and need to assign them the following value
I have 'theta', 'alpha', 'a' and 'd' in separate 3*1 matrices, is there any way to loop through the 4x4 matrices to assign them these values as you cant make a matrix of matrices .
i.e. what in other programing languages would be 3 nested for loop with a matrix foo = [M0T1, M1T2, M2T3] and accessed by foo(i, j, k), where i would be the matrix and j & k the row & column
In Matlab, you can iterate over the elements in the list directly. This can be useful if you don't need to know which element you're currently working on.
Thus you can write
for elm = list
%# do something with the element
end
Note that Matlab iterates through the columns of list, so if list is a nx1 vector, you may want to transpose it.
for i=1:length(list)
elm = list(i);
//do something with elm.
You should call the cell's content via str{1} as follows to make it correct:
for str = {'aaa','bbb'}
fprintf('%s\n',str{1});
end
Here's a more sophisticated example on printing contents of cell arrays.
str={'aaa','bbb'};
fprintf('%s\n',str{:});
No need for for loops.
EDIT:
See also: cellfun