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How can i get the possible combinations to get 20 'i's from the given vector:
dn = 0 i i i i i i i i i i i i 0 i 0 i i i i i i i 0 i i i i 0 i i i i i i i i i 0 0 i i i i i i i 0 i i i 0 i i 0 i i i 0 i 0 0 0 0 0 0 i i 0 0 0 0 0 0 i i 0 0 0 0 i i 0 0 0 i 0 i 0 0 i 0 i 0 i i 0 i i 0
My objective
1. No of possible combinations with each combination having 20 i
2. Index value of each 'i's for all combination
Example:
var = 0 i i 0 i 0 i i 0 0 0 i
Here I need posiible combinations with 2 'i's
I can form the combinations like (2,3),(2,5),(3,5),(2,7) and so on.
I think this does what you want:
var = [0 i i 0 i 0 i i 0 0 0 i];
N = 2;
result = nchoosek(find(var==i), N);
In your example, this gives
result =
2 3
2 5
2 7
2 8
2 12
3 5
3 7
3 8
3 12
5 7
5 8
5 12
7 8
7 12
8 12
Related
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I have a RGB matrix like this:
0 0 0 0 0 0 0 0
0 0 23 0 0 0 0 0
0 1 255 0 0 130 22 0
0 49 0 0 0 0 120 0
0 0 0 0 79 0 213 0
0 0 0 0 0 0 0 0
Need to trim(remove zeroes at the boundaries) this matrix to be like:
0 23 0 0 0 0
1 255 0 0 130 22
49 0 0 0 0 120
0 0 0 79 0 213
You can using sum to find rows and columns which are all zeros. Then, remove them.
s1 = find(sum(mat,2)>0);
s2 = find(sum(mat,1)>0);
mat([1:(s1(1)-1) s1(end)+1:size(mat,1)], :) = [];
mat(:, [1:(s2(1)-1) s2(end)+1:size(mat,2)]) = [];
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So I have this matrix:
0 1 0
1 0 0
0 0 0
0 0 1
0 0 1
0 1 0
0 1 1
I don't know what statement(s) I have to write to change the bottom row only so that it becomes:
0 1 0
1 0 0
0 0 0
0 0 1
0 0 1
0 1 0
1 0 1
Specifically, I'd like to swap the 1st and 2nd column of of the 7th row only.
Not only that but I'd like to write a statement that finds adjacent 1's value in a row such as 1 1 0 or 0 0 0 1 1 0 and then applies the same switching.
Suppose that the variable mat represents your matrix. use:
mat(7,[1,2]) = mat(7,[2,1]);
Where 7 specifies the row which you want to perform the swapping on, and 1 and 2 are the columns to swap.
This question already has answers here:
How can I change the values of multiple points in a matrix?
(3 answers)
Closed 6 years ago.
I want to create an array according to row number and column number.
For example :
row_number Column_number Value
1 1 5
3 2 10
4 6 4
7 5 66
The array should look like :
A=
5 0 0 0 0 0
0 0 0 0 0 0
0 10 0 0 0 0
0 0 0 0 0 4
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 66 0
Otherwise it will print zero.
3 possible methods to this regularly asked question:
1. Using the sub2ind function
A = zeros(max(row_number), max(Column_number));
idx = sub2ind(size(A),row_number, Column_number);
A(idx) = Value;
2. Calculating the linear indices manually
A = zeros(max(row_number), max(Column_number));
idx = row_number(:,1) + (Column_number(:,2)-1)*size(A,1)
A(idx) = Value;
3. Use a sparse matrix
sparse(row_number, Column_number, Value)
And then call full on that if you want to convert it to a regular matrix
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Could you help me. I want to generate matrix of '0' and '1' (for example rows 8 and columns 7; r and c). I want to specify fixed size columns (in this example fixed=3) and on it position in every execution should be all '0'. The rest should be randomly and unique selected. Here is example:
0 0 0 1 0 1 0
0 0 0 0 0 0 1
0 0 0 1 0 0 0
0 0 0 1 1 0 0
0 0 0 0 0 1 1
0 0 0 1 0 1 0
0 0 0 1 1 1 1
0 0 0 0 1 1 1
my_matrix = [zeros(7, 3), floor(rand(7,4)*2)]
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Assume that there is a matrix
m = magic(5)
ans =
17 24 1 8 15
23 5 7 14 16
4 6 13 20 22
10 12 19 21 3
11 18 25 2 9
As known, in order to change a specific values (eg: change to 0 if greater than 10) in a m×n matrix,
m(m>10) = 0
m =
0 0 1 8 0
0 5 7 0 0
4 6 0 0 0
10 0 0 0 3
0 0 0 2 9
I have a k×m×n matrix which consists of random 0s, 1s and 2s. k has iteration values 1 to 10 and will not be changed.
How can I change 1s to 0s then 2s to 1 sequentially? But kshould be unchanged. Only the values in m's and n's.
As an example of "Do it exactly the same way":
>> m = round(rand(3,2,2)*2)
m(:,:,1) =
1 1
0 0
1 2
m(:,:,2) =
1 1
0 1
2 1
>> m(m==1)=0
m(:,:,1) =
0 0
0 0
0 2
m(:,:,2) =
0 0
0 0
2 0
>> m(m==2)=1
m(:,:,1) =
0 0
0 0
0 1
m(:,:,2) =
0 0
0 0
1 0
The 3D logical mask returned by m==2 in this case can be used on any array with the same size.