Questions tagged [dot]
The dot tag has no usage guidance.
47
questions
3
votes
1
answer
34
views
Factor constants out of multiple dot products
I have expressions of the type
(-y A.A).(-y A.A).(A x).(A x) (* Example 1 *)
(-y A.A).(-y A.A).(A x) (* Example 2 *)
The number of parenthesis factors can vary, ...
- 239
0
votes
1
answer
98
views
Scalar product of vectors using dummy indices
How can I rewrite the following expression
$expr1= (A\cdot B)(C\cdot D)(E\cdot F) + (A^\prime\cdot B^\prime)(C^\prime\cdot D^\prime)(E^\prime\cdot F^\prime) +\cdots $
in terms of the components as
$...
- 95
1
vote
2
answers
137
views
Plotting a discrete set of data points and continuous plot together
I am struggling to plot discrete set of lines ( black dashed line around the black point) along with a continuous plot ( blue and yellow curves).
Following is the problem:
Basically i want to plot ...
- 169
3
votes
2
answers
228
views
Speed up dot product with shifted vector
I have to calculate multiple dot products between a vector and consecutive part of another (longer) vector, shifted at certain number of elements. Naive implementation takes about 0.1 seconds.
...
- 959
8
votes
2
answers
349
views
Dot Product and Simplification
How to simplify the expression
a b . x/((a b) . x)
Where a is a scalar and b and x are vectors.
I have tried the usual Simplify, FullSimplify, TensorExpand etc. ...
- 785
1
vote
0
answers
110
views
Why is the dot operator not just matrix multiplication?
It seems to me Mathematica does not have an inbuilt matrix multiplication operator. The dot operator fails as such, as is even noted under "Possible Issues" in its documentation it ...
- 111
2
votes
0
answers
65
views
Dot product of arrays that are members of the same list
Lets say I have a list of n arrays:
n=3;
list = Table[RandomInteger[{-10, 10}, {2, 2}], n];
I would like to calculate the matrix corresponding to:
...
1
vote
1
answer
69
views
2
votes
1
answer
59
views
Simplifying expressions with dot or non-commutative product (without the help of NCAlgebra)
I have two expressions (with dot and non-commutative product):
$f=J^T.x+J.x$
$g=J^T**x+J**x$
I want to simplify them and get the following expressions:
$f=(J^T+J).x$
$g=(J^T+J)**x$
In an attempt to ...
- 2,374
0
votes
1
answer
673
views
dot product and norm [closed]
Can you solve the following problem in mathematica program? Thank you.
Let x=(x1,x2,x3),y=(y1,y2,y3) and ⟨x,y⟩=x1y1+2x2y2+x3y3 be an inner product in a three-dimensional real vector space.
Define the ...
- 13
2
votes
0
answers
77
views
dot product of one thousand matrices [closed]
I have a time dependent matrix. In a thousand different times with the same time intervals I get the values of the matrices. Now, how can I DOT Product these thousand matrices in time order??
0
votes
1
answer
90
views
Want to multiply same matix n times using dot product
I want to multiply same matrix using dot product for n times.
U[n_]:=Apply[Dot,[MatrixExp[-I H ]],{i,0,n}]
- 35
0
votes
0
answers
89
views
Dot Product doesn't behave like normal function
I am trying to slightly modify the Dot function by treating it like a usual function, but soon I notice something weird about it.
Suppose there is a set ...
- 513
1
vote
0
answers
59
views
Take overall minus sign in front in dot product with symbolic variables
I have the following as the output of a calculation
a.b+(-a).b
and I would like Mathematica to evaluate this to zero. Is there a way to specify that for my ...
- 181
0
votes
0
answers
91
views
Weird behavior of ℏ (\[HBar]) symbol on TensorExpand
I was trying to implement some tools to do commutators on quantum mechanics, just for fun. Then I noted a peculiarity:
...
1
vote
0
answers
68
views
Symmetry of Command Dot
I would like to work with the command Dot assuming symmetry. Specifically with the order
D[v[t].v[t], t] I get the following output
...
- 131
1
vote
1
answer
307
views
Nonrectangular Tensor Encountered error with rectangular matrices
I have two matrices which are rectangular. This code works with other applications I have but not this one.
...
2
votes
1
answer
72
views
Making Dot linear also for Kronecker Products
I want to manipulate expressions like
$$\big\{(aX+bY)\otimes Z \big\}\cdot \big\{U \otimes (c V+d W) \big\} $$
so that Mathematica (10) yields
$$ (aX U+bYU)\otimes(cZV+dZW) = acXU\otimes ZV+bcYU\...
- 155
5
votes
1
answer
108
views
How can I tell `Dot` to behave automatically linear?
I would like the number $a$ to be taken out:
...
- 155
0
votes
1
answer
311
views
Trying to find the double dot product of a Rank 4 and Rank 2 tensor
I understand this question has been asked before, or something very similar to what I'm trying to accomplish at the very least, however I didn't understand much of what was happening in the other ...
1
vote
0
answers
121
views
Simplifying the dot product [closed]
Why does the code
D[x.x, x] /. {1. x -> x, x .1 -> x}
gives 1.x+x.1,
while
...
- 691
2
votes
2
answers
521
views
Distribute dot and multiplication on a sum
I have a simple problem, I would like to get the following:
In= Distribute[a.(b+c)*d]
Out= a.b*d+a.c*d
Meaning that I would like the dot product and the ...
- 125
0
votes
1
answer
48
views
How to plot two functions together when one of them needs to be a series of dots, with common labels and colors?
I have two functions that I want to plot together. I want to plot the non-linear and the linear (NL and L in my code) functions together, but I wish that the NL function is plotted as a series of dots ...
3
votes
4
answers
640
views
Dot product result has wrong dimension [closed]
I'm doing a small project and I've encountered a problem while using Mathematica. I should mention that I'm kinda new to this software, so maybe it's just something I haven't grasped yet.
Anyway, I ...
- 35
3
votes
1
answer
421
views
How to change node color in .dot file using pattern matching?
For example I have a dot file that describe a decision tree or binary tree
In the file, the color of node is always gold, so I try to change it according the number in ...
- 6,776
0
votes
0
answers
19
views
Matrix multiplication Q.W not working - Result=matrix Q . matrix W [duplicate]
When I write the code to do the dot product between two matrices, Mathematica does not compute it:
How can I get the right matrix?
EDIT
Thank you for your willingness.
- 949
4
votes
2
answers
148
views
Product but with Dot operation [duplicate]
I want to describe a way to express a chain of Dot Product like this:
m[13].m[12].m[11].m[10].m[9].m[8].m[7].m[6]
Something like
...
- 41
4
votes
2
answers
231
views
Nested Matrix Dotproduct
For a given matrix M[n] of size $ n\times n $ I want to define the following list of matrix-expressions:
...
- 49.6k
1
vote
1
answer
132
views
Importing a .dot graph file, and changing vertex label format
I worked out how (one way...) to import a .dot graph format file into Mathematica using
...
user7713
3
votes
1
answer
135
views
Dot Product of Matrices in NDSolve
How to efficiently solve a system of differential equations involving matrix dot product?
The example below is solved extremely fast when the array structure is flattened out. Is there a way to reach ...
- 407
1
vote
2
answers
2k
views
dot product not working [closed]
Im supposed to take the dot product of a function and itself. The matrix is a system of 4 equations defined to be :
...
- 11
3
votes
1
answer
357
views
Orthogonalize with a custom inner product
Bug introduced in 9.0 or earlier and fixed in 10.0
I was trying to define a custom inner product function for Orthogonalize, and have been getting some odd behaviour. Here's a MWE:
I try to compute ...
- 161
2
votes
2
answers
316
views
Generalized n-fold inner product for tensors, iteration and indexing or built in functions?
I'm very new to Mathematica, and struggling to convert one of the codes I'd written in MATLAB. I am trying to program a function for a generalised inner product between two tensors, that is for ...
0
votes
1
answer
994
views
Adding dots to an empty region of space [closed]
I want to add dots to the maze so far I know only how to get one dot on the maze. I don't know if there is way without using coordinates.
So it would look like this with the dots added
(source: ...
- 71
0
votes
0
answers
132
views
Expressing the output product using dot
I have an expression of the form Hbar.H where H and Hbar are vectors. How can I get the ...
- 365
10
votes
1
answer
368
views
TensorReduce and Dot
I'm manipulating abstract tensors with Mathematica. I have a question. With the assumptions
$Assumptions = (R | r) ∈ Arrays[{4}];
I can do two operations: ...
- 909
3
votes
2
answers
298
views
Summing matrix products
I need to compute a double sum over a weighted matrix product: $L[M]=\sum_{i,j}^{N}\Lambda[[i]]\;\omega[[i]].M.\omega^{\dagger}[[j]]$.
$\Lambda$ is a list of with N complex values(weights) and $\...
- 31
5
votes
3
answers
627
views
Bilinear Dot Function
In mathematics the matrix product is a bilinear operation
$$
\alpha A \cdot(\beta B + \gamma C) = \alpha\beta ( A \cdot B )+ \alpha \gamma (A\cdot C ),
$$
where capital letters denote matrices and ...
- 1,249
6
votes
0
answers
1k
views
Is it possible to simplify an expression in vector form, which involves crossproduct and dot product?
I often need to simplify expressions involving cross product and dot product, for example:
f = Dot[Cross[Cross[p1 - p, e1], Cross[p2 - p, e2]], Cross[p3 - p, e3]]
...
- 695
1
vote
1
answer
2k
views
Using the Norm Function
I am trying to take the norm of a general vector and show that for vectors, v,w, that
Norm[v cross w]^2==Norm[v]^2*Norm[w]^2-(v dot w)^2
In Mathematica, here are my steps:
...
- 157
2
votes
2
answers
780
views
Pulling out a prefactor from a dot product
I have three complicated vectors u, v and w as well as three simple prefactors ...
- 143
6
votes
3
answers
570
views
Factor out the scalar multiplier for the dot product of 2x2 matrices
If yy and zz are 2x2 Hermitian matrices, is there a way that I can mark them (with a property?) as Hermitian so that Mathematica can assume that it can factor out and simplify scalar multipliers from ...
- 271
1
vote
1
answer
247
views
Unexpected inefficiency when calculating matrix product by Dot
There is an unexpected inefficiency when I calculate matrix product by Dot. The only relevant part of my code is presented as follows:
...
- 425
5
votes
2
answers
740
views
Dot product for lists
Suppose we want to get the dot product for the following lists aa and bb, whose elements (a, ...
- 1,550
22
votes
3
answers
1k
views
Why is calling Dot with many arguments so inefficient?
Say I want to multiply a reasonably large list of symbolic matrices.
...
- 1,249
14
votes
1
answer
464
views
Why does partitioning increase Dot execution speed?
I have noticed that multiplying a list of matrices can be significantly sped up by partitioning the list, calculating the product of the partitions matrices, and then multiplying the results.
...
- 1,249
4
votes
1
answer
2k
views
Draw grid with points
How would I draw a grid with dots on specified intersections? The image below shows the basic idea:
If I wanted to label the grid lines with index numbers or letters, how would I do that?
- 4,048