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Questions tagged [syntax]

Questions on correct (or improved) formulation of Mathematica code to achieve particular results. Use this tag (not "symbol") for questions about all those odd @@ /@ # & and ~ characters.

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42 views

How to use === with condition?

I have two expressions, and they are same when k is positive and x is non-zero real number. Below code gives me ...
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0answers
95 views

Hyperbola ContourPlot missing input

I'm trying to plot a hyperbola using ContourPlot, but I can't understand what I'm missing on its call. The error says it's incorrect syntax, although I can't see any errors. ...
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30 views

Shorthand of Get[] [duplicate]

I thought that << expr was just a shorthand form of Get[expr]. I have now found that it clearly isn't. Namely it holds <...
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0answers
43 views

Solve not working now, but did befoe [duplicate]

I did this Solve earlier and it worked. Why is it not working now? I tried other solves after this one, and did not work, also. I tried creating a new notebook, and it did not work there, also.
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3answers
42 views

Understanding Solve output [duplicate]

In Solve output for such as: Solve[r^2 - 6 r - 3 s^2 + 8 s Sqrt[r] == 0 && 0 < s < 1, r, Reals] Where in the documentation do I learn how to read ...
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46 views

RSolveValue syntax

Can't see anything wrong with this: sol4 = RSolveValue[{a[n + 1] - 1.2*a[n]*(1 - a[n]) == 0, a[1] ==0.1}, a[n], n] But I just get an echo from Mathematica
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40 views

Simple assignment results in “Tag times in 1 Null is protected” error [duplicate]

I've read multiple topics about "Tag times is protected" error, but none of them were struggling with the same problem I am (or maybe I just didn't see it), so I'm asking for help since I'm unable to ...
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25 views

What does Solve output with # and & mean [duplicate]

I tried to solve a symbolic equation using Solve and in that I get expressions like #1^5 &, 1 what does this mean? I ...
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51 views

Assumptions work for simple function but don't work for complicated function

Suppose the function f1[s1uppern_, s1lowern_]= I Sqrt[s1uppern - s1lowern]/(s1lowern - s1uppern)^(3/2) I want to simplify it assuming that ...
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50 views

Which of the following inputs is correct for the desired operation?

sorry for another (very likely) dumb question, but I'm having trouble telling which of the following (if either) yields the desired operation. What I'd like is to define a function: $$ud = u(f/2) - \...
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375 views

(Basic Question) How to use nested functions properly?

UPDATED PORTION OF QUESTION AT THE BOTTOM First, let me apologize for two things: 1) I'm very new to Mathematica, so this question is certainly very stupid, 2) I looked for the solution to this both ...
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71 views

Indicate level with Replace [duplicate]

Replace[{{x^2, Sqrt[x]}, {x + 1, x - 3}}, f_[x__] -> f, 1] Level 1 of Replace works here as expected with output {List,List} ...
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62 views

Relative speed of definite integration and indefinite integration with substitution

Suppose some complicated integrable function $f[x]$ (possibly depending on parameters). One can perform definite integration over $x$ inside the domain $[a,b]$ by using construction ...
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793 views

'Cannot be followed by..' error when implementing while loop

I am trying to implement the following (iterative) scheme (a preconditioned conjugate gradient method): ...
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1answer
91 views

How can I make ListPlot use my iteration as the x coord?

I have some code that takes a list of energies, plugs them into a set of recursion relations and numerically solves for each energy (15 energies total) and for each n(modes, 21 total) ...
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0answers
93 views

Solve / Reduce runs overnight - should I keep waiting?

I'm pretty new to Mathematica and I'm trying to solve a system of two equations, but both Solve[] and Reduce[] have been running ...
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0answers
23 views

Problem with PolarPlot and Table [duplicate]

If I have a set of numbers, for example grid = N[Table[n^2/2, {n, 3, 24}]] And want to plot that as circles I can either use Graphics[] and Circle[], or ...
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0answers
46 views

Syntax question for declaring variables [duplicate]

I have a very basic syntax question for declaring $X_{hb}$ a variable. f[Subscript[X, hb_]] := Subscript[X, hb] In mathematica instead of writing the ...
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30 views

I would like know why “&” came after “FrontEndToken[”New"] here [duplicate]

I am a newbie to this Mathematica world who lives in South Korea, which is not a desirable place to have people to discuss Mathematica. So I came here, even though this question may look very simple ...
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0answers
60 views

Solving Integral -syntax or interpretation problems

WA interpreter achievement not well this entry from Mathematica, steps need to see the full resolution input WA ...
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1answer
45 views

Possibly syntax errors? [duplicate]

trying to graph, however graph is blank when i enter it. Please help! ...
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0answers
49 views

Treating expressions as symbols [duplicate]

I'm trying to do something like this: test = {x, y}; With[{test[[1]] = 3}, x/y] However, the following error is printed: With::lvset: "Local variable ...
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0answers
59 views

What makes items with head `Function` different?

I apologize beforehand for the muddleheadedness of this question. It reflects the fact that I'm trying to interpret outward "behaviors" of Mathematica expressions without having any understanding of ...
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0answers
45 views

What does a single @ do? [duplicate]

I have a simple expression: N@Log2@g[2048] I understand that N is Numerical value , that a function called g is being ran with 2048 as its first argument. But ...
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0answers
51 views

Assigning to a variable with a computed name [duplicate]

I wish to assign about a dozen variables to complicated expressions. to ensure that the correct variable is assigned to the correct expression, I’d like to do something resembling ...
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1answer
59 views

Help for properly writing simple derivative expression

I need help to write the following expression (only 1 iteration): f(x) = ...some basic function... f[X0,...,Xp] = f(p)(x0) / p! What I have so far: ...
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1answer
89 views

How to embed a math expression in a text? [duplicate]

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0answers
46 views

How can I mix // with a function of two arguments? [duplicate]

I often find myself using // when playing around with expressions, but it is always cumbersome to have to switch to the full notation just to apply a function of ...
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0answers
169 views

My “N” turned red randomly [duplicate]

For some reason my N function showed up in red even though I haven't noticed it in that color before. The color actually makes the code much more readable but I just don't know if I should be alarmed ...
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0answers
205 views

Meaning of backtick in conjunction with units [duplicate]

In this fragment from an equation solution the backtick is used twice: ...
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0answers
225 views

Using Table[ ] vs using Do[Append [ ] ] [duplicate]

Is it generally better/faster to use the Table function over using Do[Append []]? For example, I have this piece of code: <...
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0answers
26 views

Incorporating Built-In Function Options/Parameters into Shorthand [duplicate]

Shorthand syntax provides an alternate way to apply functions and, in many cases, improves readability. A simple example would be ...
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0answers
163 views

The /. syntax in numerical methods [duplicate]

I have an analytical approximation method for solving an ODE and want to compare this to an NDSolve solution, but the syntax is confusing me. To get the solution from NDSolve, I define the ODE as eqn ...
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1answer
126 views

Why does Eigenvalues[matrix I defined] not work? [duplicate]

This is the code I have in my mathematica notebook. I want to find the eigenvalues of the matrix I created called Hmatrix as defined below. However when I type Eigenvalues[Hmatrix] I get the Hmatrix ...
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1answer
2k views

What is wrong with this Cobweb plot [closed]

Something is wrong with my cobweb plot code but I couldn't figure out where do the mistakes come from. So basically we have the iterative map $x_n == x_{n-1}^{2} - 3 \mu$. I would like to draw a ...
-1
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3answers
89 views

How to remove a line from the ListPlot?

Consider the following ListPlot: ...
-1
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1answer
59 views

Operations between sets of integers [closed]

sorry it was impossible to put the code in Latex, he said that there were problems of indentation, I put the image
-1
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1answer
102 views

How to make sure input is an ODE

I'm having trouble wrapping my head around why this isn't an ordinary differential equation. ...
-1
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1answer
85 views

Syntax Error for the following code

I have the following code in mathematica ...
-1
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1answer
140 views

What is a proper way to express derivatives with respect to a symbol? [duplicate]

Mathematica's default way of representing derivatives is to express them with respect to a function's input slot. But what if I want to use the chain rule? To replace df(x)/dx with df(0.5 y)/dy 0.5, ...
-2
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1answer
218 views

Sign of a symbolic expression as a function of parameter values

I need to know the sign of the following expression for p[t] = z/(1-a), as a function of the parameters {a, b, c, z}: ...
-5
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1answer
1k views

Split dataset based on the first column [duplicate]

I have a dataset which I want to split based on the first column. The data looks like this ...