# Questions tagged [indexed-variable]

Questions about indexed variables and related alternative methods to allow assigning indexed names to objects.

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### Defining custom operators for indexed objects [closed]

I have some symbolic indexed objects $A_i$, $B_{ij}$, $C_{ijk}$, $D_{ijkl}$, etc. I want to define a symbolic differential operator $\partial_{xy}$ that acts on these indexed objects in the following ...
1 vote
51 views

### About NMinimize with an array of variable

I was trying to test NMinimize on $$\int_0^1 (a+b(cx+d))^2 dx$$, then I guess it should be minimized when the integrand equals 0. It works fine when the integrand is only (a+bx)^2, I use the code: <...
• 13
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### Lorentz indices contraction

I have a complex expression involving second-rank tensors and Kronecker Deltas. How can I instruct Mathematica to utilize the Kronecker Deltas and perform proper index replacements? For example, ...
• 173
105 views

### Using Indexed variables in Compile?

This follows a: useful post about Compile from about 10 years ago In that post there is a comment: You can not really use indexed variables in Compile, although it may appear that you can. For ...
• 4,510
110 views

### Symbolic Indexing on Symbolic Arrays

Is there a way to use symbolic indices on symbolic vectors? The most barebones example I can think of is the following: aV = Array[a,3]; aV[[m]] which evaluates to ...
• 131
1 vote
65 views

### How to extract manipulated indexed variables from Manipulate

I am struggling with getting values of variables that are manipulated with Manipulate: The code: ...
• 3,962
1 vote
52 views

### Update some elements of a symbolic matrix

I am trying to build, update and manipulate a binary matrix in an optimization problem using NMinimize. The variable to be optimized on is a vector ...
• 185
71 views

I am interested in the most efficient way to impose assumptions on indexed variables. In the following stylized problem, the following code ...
• 187
82 views

71 views

### Taking a Part of a Part of a Variable

Say I have Part of a variable x. Part[x, 1] Then, I'll get an error message, as the ...
• 1,595
71 views

### Naming indexed output streams

I need to write into multiple files in a Do loop. Hence, I tried to open multiple streams: ...