# Tagged Questions

For questions relating to assignments to symbols, patterns, or expressions.

53 views

### Assigning to the “local” version of a symbol

Compare Manipulate[c[1] = 1; c[1], {c[1], 0, 1}] with Manipulate[Do[c[i] = 1, {i, 1}]; c[1], {c[1], 0, 1}] The first case ...
117 views

### Altering values in Manipulate with dynamically generated controls

I have a Manipulate whose controls are generated based on a parameter in a containing Manipulate: ...
106 views

### DownValue assignment using Apply

Why does assigning a DownValue using Apply, e.g., ...
335 views

### Assign a randomly generated list to variable

Bug introduced in 10.0.0 I don't know if this is a silly question, but it really baffles me. So please help me understand this behavior. ...
308 views

### Is there any way to assign multiple values?

I am looking for something like "byref" assignment in programming languages. Let's assume I have: x1=x2=....=xn if I want to change their values ( say to 3 ) I need to set all of them like: ...
127 views

### Assign output of solve to variables [duplicate]

I have this input: Solve[x^2 + 3 x + 2 == 0, x] which gives this output: {{x -> -2}, {x -> -1}} I want the first x ...
57 views

### Why is it not allowed to define vectors of variables in a scoping construct?

The following command assigns 1 to a, 2 to b and 3 to c: ...
78 views

### Trouble to assign solution of differential equation to a function

I have written a function to Solve the following differential equation where the number n (called in my code Nphoton) is a variable. Nevertheless I have troubles to assign the solutions ...
45 views

### How do I assign a formula to a variab [duplicate]

I want to compute equations and assign them to variable. This is a wxMaxima program that calculated symbolic PID gains for an integrating first order system ...
52 views

### How to get Symbol[“x”]=3 to work [duplicate]

This is probably a really simple one, but I'm stumped. I want Symbol["x"]=3 to work just like x=3. However I can't figure out ...
82 views

### Edit built in symbol

I would like to add new attributes to built in symbols (e.g. ElementData or PolyhedraData) so that I can still call the symbol ...
101 views

### How to name a variable with the value of another variable?

A simple but very important (at least for me) question. In some languages for defining a variable, for example, we can do: i=10 "d"&i=30 So I have defined the variable d10, and... d10=30 ...
70 views

### Can Array work as Loop? [closed]

I got Mathematica code from my friend: ...
45 views

### Evaluating an expression a second time returns wrong result

I have the following code: ...
69 views

### Maximum number of literal values for SetDelayed?

Under what circumstances should I expect Mathematica to turn a delayed assignment into an immediate assignment? I have put together a minimal example (available here) which demonstrates this behavior. ...
1k views

### How to implement the Observer design pattern?

As a programmer with a history with procedural languages, the Observer design pattern inmediately springs to my mind when attacking certain class of problems, mostly UI/notifications related. A ...
238 views

### How to copy a function by value?

I need to change a function symbol multiple times by assigning another symbol to it, but when I'm trying to do that the symbols overwrite each other. I'm assuming this is because the assignment is by ...
47 views

### Questions regarding DictionaryLookup of Mathematica

a. Make a function longest[lang_] that gives the length of the longest word in the dictionary of lang. You should get ...
108 views

### Few quick Mathematica questions about Dictionary

a. Get the list whose elements are of the form {language,number of words in dictionary) I tried this, and it gave me the number if words in dictionary, but I don't know how to get the language part: ...
87 views

### Evaluating an expression assuming a value for a variable only in the local context

Imagine we wish to evaluate some expression like NIntegrate[x^2*q,{x,0,100}] assuming some value for q like ...
33 views

### How to assign a list of subsript?

I want to assign Subscript[C,i] by mapping a specific list. For example, the list is {1,2,3,4}, and I want to assign 1 to C1, 2 to C2, 3 to C3 and 4 to C4. How should I do? Many thanks:)
139 views

### Bare symbol invocation fails but not if used with an argument

How to achieve the following behavior on a symbol f? Background: The main goal is to use the symbol to tag an abstract data structure where downvalues are used to store information. Only defined ...
79 views

### Circumventing the default scoping: Assign a variable inside a function [duplicate]

I'm currently trying very hard to assign a variable inside a function. Therefore I'm using a function like this, which should reassign a predefined variable. ...
62 views

### Replacing multiple instances of a symbol with different variables and assignments

I have an expression of the form: expr=x+y+n+Sin[n]+n^2 I would like to replace each of the variables n with a different ...
129 views

### Associate the elements of a table

I have a table form as: table = {{a, 6}, {b, ff}, {c, 2}} I want to associate the first element of each pair from the table to the second element of the pair as ...
57 views

### storing rescaled images in new variables

I'm trying to assign random image files that undergo rescaling to a list of variable names. The images I'm trying to assign are the result of mapping the ImageResize function of two arguments to the ...
123 views

### Automatically assign solutions to equation as constants

Consider the following code: ...
274 views

### Understanding Function and Variable in Mathematica for beginner [closed]

I'm reading the book of Leonid Shifrin, and I love the way the book explains the core in Mathematica. As everything is an expression, now I understand that, there ...
116 views

### Using a variable to tell Mathematica which existing variable to manipulate

I have an estimation routine I have coded up, I want now to do some tests on it where I pick a particular parameter and run the estimation for differing values of that parameter. What I want is to be ...
153 views

### Assign variable's value programmatically

Not easy to explain what I'm looking for, so please sorry if I'm not so short. Having many variables to be managed in several different combinations, I need to automate the assignment of preset ...
133 views

### Assign one button to two variables

I am trying to use the one button to assign to two variables. Here is an example of how I want it to work. expression: ...
413 views

### Integral of Lorentzian yields different results depending on when parameter assigments are made

I'm evaluating the integral of a Lorentzian, which I know equals one. First I define the function and evaluate the integral in two slightly different ways. Surprisingly, I do not get the right answer ...
166 views

### Getting mesage: Set::setps assignment is not a symbol

Please, tell me what is the issue with the following code? Dimensions[Subscript[R, 2]] {201, 161, 53} ...
105 views

### Two quick Mathematica Questions about the dictionary

Question1: Get the list of pairs of the form {language,number of words in dictionary}. Call this list langlength What I did was this: ...
179 views

### How to ignore list elements when extracting with pattern matching

If I have a simple list, say {1, 2, 3}, and I want to extract a subset of the elements, what is the correct syntax? e.g. { i, _, j } = {1, 2, 3} I want i = 1 ...
295 views

### Why does list assignment with a packed array result in unpacked values?

This is another question on the design choices in Mathematica. I understand that without direct reply from the developers it may not be possible to give a definitive and exhaustive answer to "why" ...
151 views

### Assigning numerical values to constants results in complex coefficients in Equations of Motion

I am using Mathematica to get the Equations of Motion (EOM) for a mechanical system (using Lagrangian Mechanics). While I get the EOM in symbolic form, on introducing the following code for assigning ...
64 views

### Extracting function variables from a list [duplicate]

Evaluating the following func[x_, y_] := x^2 + y^2 listn = {{a, b}, {c, d}, {e, f}}; Map[func[##] &, listn, {1}] yields {func[{a, b}], func[{c, d}], ...
110 views

### Choosing an initializer list in With

I'm trying to have several initializer lists in a With function and choose which one I want to use. So far I have this: ...
225 views

### Assign variables automatically to a function

Lets consider that I've this function: fn = a*x^2 + b*x + c; The idea here is to assign automatically the variables a, ...
260 views

### How to replace a variable that was assigned a value before

Question How to make the replacement $f[x] \to f[y]$ for an abitrary function $f$ if $x$ was assigned a value before? Example 1 How can I make the replacement $x +1 \to y + 1$ if I have assigned ...
152 views

### Different behaviours of Default Argument

I don't really understand the behaviour of Default Argument. If I execute this command in Mathematica: In: {f[a], f[a + b]} /. f[x_ + y_.] -> p[x, y] ...
138 views

### direct assignment to the element in a Table

I have already asked a related question here why set values in this way doesn't work? But I think I have to write the question which I encountered explicitly? ...
185 views

### why set values in this way doesn't work?

question is as follows define a list ttt={1,2}; and if I set values in this way {ttt[[1]],ttt[[2]]}={3,4} then the value ...
335 views

### Triggering actions when a variable is set

Some built-in variables trigger actions when their values are changed: ...
110 views

### Can I put subscripted parameter values into a package?

When defining packages, can I put parameter values alone or along with functions into a package in subscripted form? ...
116 views

### Using With in combination with Graphics [duplicate]

Assume that we are given a symbol p={x,y} which should represent a 2D point. If x and y have ...
148 views

### How to mix Unevaluated property of function arguments with expression assignments?

This is a follow-up to my (solved) question How to distribute a generic function of two arguments (without evaluating the arguments) Say, I have a binary function ...