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I have 3 signals:
a = ecg(1000); // clean ecg with no noise
b = a + noise1; // with noise component on the ECG
c = a + noise2; // a,b,and c have the same dimension (1000x1)
now, i want to put the concatenated signal onto a single variable, x, so that the output of x would be:
x = a concatenated with b; b concatenated with c;
If by cascading you mean concatenating, simply do this:
x = [a b c];
This simply pieces a, b and c together so that they are one signal and the three signals are side-by-side each other. Doing ecg(1000) creates a 1 x 1000 vector. Assuming your noisy signals after that respect the same dimensions, then the above syntax should hold.
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I loaded in the 1000x1 .txt file but I need to make it 100x10? How do I do this in matlab?
Thanks
Reshape should do this for you. https://www.mathworks.com/help/matlab/ref/reshape.html
But you haven't explained any criteria regarding what the change of dimensions is based on. So, it may not be exactly what you want.
You can use the reshape function to do this. In the example below I created a column vector x that is 1000 x 1 containing numbers that ramp from 1 to 1000. I didn't know what order you wanted the rows and columns populated, so I created variables x2 and x3 with the two variations, you can choose the form that fits your needs.
x = (1:1000)';
% x2 is created with one column at a time
x2 = reshape(x, 100, 10);
% x3 is created one row at a time
x3 = reshape(x, 10, 100)';
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In a sample code I have X(1:n, 1)
I don't understand how it works
n=3 in a sample
Is it a matrix? but isn't () used for indexing so how it's a double index?
I imagine that your X is a two-dimmensional matrix. Generalizing, it can be said that to access the elements of a matrix is done with: X(n,m).
The common case is to get one single number, in that case n and m are integer numbers. But you can also pass vectors to n and m positions and that way extract a submatrix from the original one.
As an example:
X = [1 2 3; 4 5 6; 7 8 9]
X(1:3,1) = [1; 4; 7]
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I would like to pick two different random elements from given array with their positions. Similar like with datasample, but with datasample there is a possibility of picking the same element twice.
I could use while loop or similar, but I suppose there is an easier way to do it.
Say you have a matrix A:n by m, you can choose two elements at random as following,
A=[2 7 8;5 4 6;8 3 11];%given array
[n m]=size(A);
x=2;%two different random elements
i=randperm(n,x)%row index for x elements
j=randperm(m,x)%column index for x elements
A(i(1),j(1)) %First random element
A(i(2),j(2)) %Second random element
If you try this you could get something like,
i =
2 3
j =
2 1
ans =
4
ans =
8
the code can be further simplified but just wanted to make it clear. Please let me know if you have any additional questions or require further clarification.
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I need to start with the highest value in the matrix (i,j). Then, go backwards to one of positions (i-1,j), (i, j-1), and (i-1, j-1) depending on the direction of movement used to construct the matrix. This method is used throughout until a matrix cell with zero value is reached.The above image shows what I want, I need to trace those marked in blue. I know there is a max function in matlab.
If I understand what you try to do...
Suppose M is your matrix:
result=[];
[~,ind]=max(M(:));
[r,c]=ind2sub(size(M),ind);
result=[result; r c];
while M(r,c)~=0
[~,f]=max([M(r-1,c),M(r,c-1),M(r-1,c-1)]);
switch f
case 1
r=r-1;
case 2
c=c-1;
case 3
r=r-1;
c=c-1;
end
result=[result; r c];
end
Then, result is a 2 x n matrix, where each row is the indexes of one step- from the upper to lower.
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I have two numbers a and b such that a*a*b=constant. How can I find all as and bs which satisfies this equation?
Can I have a graph for example for a versus b?
Actually, I am looking for a relationship between a and b, as an example an equation for their graph mentioned before.
Let c be the constant, then
a*a*b=c
We find an explicit solution for b(a) by
b = c / (a^2)
Now we can easily plot b vs. a. E.g. for c=1 :
Specify which points for a you want to plot. E.g. a = -2:0.1:2
Calculate b: b = c ./ (a.^2);
Plot b vs. a: plot(a,b);
All together:
c = 1;
a = -2:0.1:2;
b = c ./ (a.^2);
plot(a,b);