New answers tagged matrix
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Symbolic scalar-by-matrix derivative
I tried the NCAlgebra package:
<< NC`;
<< NCAlgebra`;
SNC[X, A]
NCGrad[tr[tp[tp[X] ** A] ** (tp[X] ** A)], A]
And ...
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4
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Accepted
Inverse of a matrix with symbolic variables
Replacing all machine-precision numbers by exact numbers:
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0
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How to solve this equation of n-order matrix?
Does this work for you?
ident[i_, j_] := KroneckerDelta[i, j]
jmat[i_, j_] := 1
mmat[i_, j_] := (k - \[Lambda]) KroneckerDelta[i, j] + \[Lambda]
then:
...
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4
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Timing for generating long matrix
This seems to produce the correct result and is much faster for small values of n.
...
- 94.7k
4
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Accepted
Timing for generating long matrix
I suspect you only want to optimize the last line, i.e. I haven't bothered speeding up s. In what follows I'll use the first 1000 x 1000 submatrix to show some ...
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How to approximate a function using B-spline interpolation?
B splines are already built into MMA.
To expand Sin[x] over the region 0 o 2 Pi into B splines of degree d=3 we choose a basis of b splines with uniform knots at a distance of 1/(d+1):
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8
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Accepted
How do I create and combine column matrices from lists
Mathematica uses the list for almost everything. You can think of a list as a row for now for purposes of making matrices.
So when you write ...
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Is there a way to apply a two-argument function to matrices?
Is the following application of MapThread with a level specification what you are looking for?
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3
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How does NDSolve treat matrices?
An alternative to Indexed to deal with matrices is to prevent f from evaluating until a matrix value is substituted for ...
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4
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How does NDSolve treat matrices?
I think that what you want to do with your broken code :
f[rho_,t_]:=Table[rho[[n,m]],{n,1,2},{m,1,2}]Cos[t]
is something similar to this code :
...
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How to Create an Efficient Word Square Algorithm?
I have created an algorithm that takes about 2.4 seconds to find the word squares for "hair" and 10.5 seconds for "dogs".
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NDSolve: there are more variables than equations, underdet
There are several typos in the code. First, initial data array probably should be in a form
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4
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Derivative of quadratic form in NCAlgebra
As noted in the documentation of NCGrad:
IMPORTANT: The expression returned by NCGrad is the transpose or the
adjoint of the standard gradient. This is done so ...
- 1,541
2
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Looking for a efficient way of solving a matrix which is function of some variable
Maybe you could use FindRoot? The trick is to know how to differentiate the determinant of a matrix, which is:
$$\frac{d \det (g(x))}{dx} = \det\left(g(x)\right) \
\...
- 123k
1
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Total Spin Matrix Squared (Casimir Operator)
Compute Dot[#,#] for each element # of the list and then sum up the results?!
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Looking for a efficient way of solving a matrix which is function of some variable
The type of dependence in f is critical here. For your example, it amounts to calculating a generalized eigenvalue.
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6
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Invert a generic n x n matrix
Clear["Global`*"]
For the given example of DiagonalMatrix[n*Range[n]], the Inverse...
- 119k
1
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Help with equation within adjacency matrix
You could use, for instance:
{i, j} = Transpose[List @@@ edges];
truedistance = scalefactor Sqrt[Total[Abs[coordinates[[i]]^2 - coordinates[[j]]^2], {2}]];
If you ...
- 94.7k
2
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Accepted
Insert a dynamic vector into a matrix
Maybe like this:
NN = 3;
n = 6;
Flatten /@ (IdentityMatrix[n] /. 1-> Cs[NN])
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Insert a dynamic vector into a matrix
I think you need to minimally modify your code using Sequence in a ReplaceAll.
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0
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Test First row of matrix
I think it may be better to use something like Association, but since this question is from 2012, but Association is introduced ...
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