# Questions tagged [dot]

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### Patterns with Dot [duplicate]

I would like to understand the behavior of Dot to build patterns with it. Could someone tell me what is going on in these examples? ...
• 998
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• 105
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### Plotting a discrete set of data points and continuous plot together [closed]

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 ...
• 179
269 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
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### 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
121 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
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### 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
71 views

### Clarification of the $MemberQ$

There are a number of expressions: ...
• 2,404
68 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 ...
• 2,404
756 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
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??
111 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}]
92 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 ...
• 543
1 vote
69 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
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### 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
69 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 ...
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1 vote
338 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. ...
75 views

• 1,249
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### 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]] ...
• 735
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: ...
846 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
581 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
254 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
769 views

### Dot product for lists

Suppose we want to get the dot product for the following lists aa and bb, whose elements (a, ...
• 1,560
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
467 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. ...
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