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Questions tagged [faq]

Frequently Asked Question – a tag for original questions which have a multitude of duplicates

5
votes
1answer
132 views

With vs. Block scoping of parameters for Plot

A very basic question.. Why does Block work, but not With, to specify value of a parameter for a function to be plotted? ...
3
votes
1answer
77 views

How to preserve scaled circular shapes when combining graphics?

The following code g1 = Graphics[{Thickness[0.01], Line[{{0, 0}, {10, 10}}], Disk[{5, 3}, Scaled[0.1]]}, Frame -> True] produces the following output I then ...
7
votes
2answers
629 views

Why changing to float-point value does't improve the speed?

I am testing the first tip of this article Use floating-point numbers if you can, and use them early. I've compared a pair codes and finding it's not helpful to use the float-point number during ...
4
votes
3answers
175 views

Keep only rules that replace integers with other integers

Let's say I have a list of replacement rules: List1 = {2 -> 3, b -> 5.5, 6.57 -> 2, 3 -> 4.5, 1 -> -1, 0.03 -> 0.5, 9 -> a} The desired ...
7
votes
2answers
225 views

Grid with Frame->All: How to not draw frames around empty cells?

If I have a grid of values that doesn't divide evenly, for example a list of 17 values, and split it into a 7x3 grid, then draw frames around each element: ...
11
votes
4answers
1k views

Capital Letters that are built-in symbols

I'm trying to search for an answer to "What is the complete list of single capital letters that represent built-in Mathematica commands, symbols, or uses?" For example: C, D, E, I, N, O Is this ...
8
votes
1answer
437 views

Package functions and symbolic calculations

I'm writing my package (.m) in Mathematica and when I call the function it returns 0 instead of a right output. Here's my code: Package.m ...
2
votes
1answer
655 views

Piecewise Function, Explanation of Extra Case

Consider: Can someone explain why the 0, True occurs? As a second question, I like to fill the endpoints as follows: ...
24
votes
1answer
15k views

What do the X and Y axis stand for in the Fourier transform domain?

In Wolfram Mathematica the function Fourier has the following declaration Fourier[list] And after a list is given to the ...
49
votes
3answers
4k views

Changing Values in an Association using Map

I am trying to change the value of one key in an association based on the value of another key in that association. So if my association starts as: ...
8
votes
2answers
2k views

A problem about function N

Toady,I have a problem about N,described as below: For example N[1/3, 5] (* ==> 0.33333*) and ...
5
votes
4answers
657 views

Efficient method for Inserting arrays into arrays

This is strongly related to the following Questions: Looking for a way to insert multiple elements into multiple positions simultaneously in a list Building matrices by attaching vectors (columns) ...
16
votes
5answers
10k views

Matrix Multiplication in context of row and column vectors

I've been looking at some matrices in Mathematica and I've noticed something very weird: they're extremely temperamental when it comes to dot products! For example, if I have the following, ...
15
votes
2answers
5k views

Error entering equation in DSolve

I entered a command incorrectly as follows: DSolve[{y'[x]=y[x]},y[x],x] I am now experiencing: ...
31
votes
3answers
23k views

How can I plot implicit equations?

If you enter the following into Wolfram | Alpha, you get nice graphs: graph 4 x^4 + y^2 = 2 How do you do this in Mathmatica? I realize that these are not ...
13
votes
5answers
8k views

How to plot periodic function's graphic?

How to plot periodic function's graphic? For example, $f(t) = t$ when $-5<t<5$ and $f(t+10) = f(t)$. ...
4
votes
2answers
1k views

Mathematica not plotting whole logarithmic function

I am trying to use the following input Plot[Log[E,x+1],{x,-50,50},PlotRange->50] however the output is: How can I adjust it so the line goes down to the <...
8
votes
1answer
474 views

Preventing cell height adjustment when rotating 3D graphics

I have a large dataset of scattered x,y,z coordinates. I am trying to use ListPointPlot3D to identify outliers in 3D. This involves generating a plot and then ...
12
votes
2answers
486 views

Unexpected behavior of rule matching a pattern

I am a beginner exploring the world of Mathematica. I expected the following code T[6, 5, 4, 1, 2, 3] /. {T[a___, 1, b___] -> Length[List[b]]} should return ...
9
votes
3answers
7k views

Replace very small numbers by zero in the output of a list

I have a long nested list, but many elements are numbers of order 10^-18 or less, e.g. ...
23
votes
5answers
4k views

Extracting variables from an expression

I'm looking for a way to extract a list of variables from an expression, for example with an input like: ...
46
votes
4answers
2k views

Enforcing correct variable bindings and avoiding renamings for conflicting variables in nested scoping constructs

Using global variables the following turns an "expression" into a Function: expr = 2 x; Function[x, Evaluate[expr]] Of course ...
14
votes
4answers
1k views

Splicing a list of arguments into a function with Sequence

Not sure if this has been asked, but I have a fairly simple operation that I don't know the syntax for. Say I have an array with some values, and a function f that accepts an arbitrary number of ...
445
votes
37answers
94k views

What are the most common pitfalls awaiting new users?

As you may already know, Mathematica is a wonderful piece of software. However, it has a few characteristics that tend to confuse new (and sometimes not-so-new) users. That can be clearly seen from ...
33
votes
4answers
8k views

How to modify function argument?

Usually in programming languages, function arguments are normal local variables, which can be modified. Is this not true in Mathematica? ...
7
votes
1answer
3k views

White regions in DensityPlot — is this a bug with ColorFunctionScaling?

Is this a bug with ColorFunctionScaling? When I try to supply my own ColorFunction Mathematica seems to partially ignore it, ...
39
votes
3answers
11k views

How do I work with Root objects?

I want to solve the trigonometric equation : $$(3-\cos 4x )\cdot (\sin x - \cos x ) = 2.$$ I tried Solve[(3 - Cos[4*x])*(Sin[x] - Cos[x]) == 2, x] It returns the ...
26
votes
4answers
26k views

How do I identify the source of a “Tag times protected” error?

I have some code that looks like Table[ a = 1; b = {2, 3} c = i;, {i, 2} ] which gives an error: Set::write: Tag Times in c {2,3} is Protected....
18
votes
3answers
5k views

How do I convert an argument list to a sequence of arguments?

I think this is a basic question, but I am having difficulty finding the answer in the documentation. Thread is not what I am looking for, I think. Suppose that I ...
10
votes
1answer
573 views

Confused by (apparent) inconsistent precision

$$ e^{\pi \sqrt{163}} \approx 262537412640768743.99999999999925 $$ E^(Pi Sqrt[163.0]) N[E^(Pi Sqrt[163.0]), 35] NumberForm[E^(Pi Sqrt[163.]), 35] returns <...
26
votes
6answers
3k views

How are parameters evaluated for a Plot in Manipulate

I am trying to get my head around how Manipulate evaluates functions in a Plot. I have read the introduction to Manipulate, and introduction to Dynamic, but I still ...
23
votes
3answers
736 views

Nested definition: How can I define a function with a passed-in expression?

Here's a simplified version of what I'm trying to do: ...
33
votes
1answer
1k views

Why are all the lines commented when I create a Mathematica script?

When I created a Mathematica script, I found that all my lines were commented out (when opened with vi or gedit or any other ...
11
votes
2answers
2k views

Evaluating an If condition to yield True/False

I would like to decide whether an option passed to my custom function has the value Automatic or something else. This is my attempt: ...
40
votes
4answers
3k views

Function in Table

I need a table with the elements made of pure functions and list elements. This is a simplified example: I need a list as: ...
45
votes
7answers
67k views

Assign the results from a Solve to variable(s)

I understand Mathematica can't assign the results of a Solve to the unknowns because there may be more than 1 solution. How can I assign the 4 values of following result to variables? ...
38
votes
4answers
3k views

Can a function be made to accept a variable amount of inputs?

I have a function that takes two inputs and processes them for a single output. What I need is one that can take a varying number of inputs. and process them to a single output. Is this possible in ...
10
votes
2answers
833 views

Programming with Dynamic

I don't understand the following: f[a_, b_] := a + b ls = {1, 2, 3}; MapThread[f, {ls, {10, 20, 30}}] This yields ( as expected ) {11,22,33} If I change ...
11
votes
2answers
739 views
4
votes
1answer
660 views

Change the height of a function being plotted

How do I alter the height of any function plot using the Plot function? Mathematica seems to limit the height of the plot up to the range of a function and distort ...
21
votes
7answers
1k views
47
votes
6answers
10k views

Finding real roots of negative numbers (for example, $\sqrt[3]{-8}$)

Say I want to quickly calculate $\sqrt[3]{-8}$, to which the most obvious solution is $-2$. When I input $\sqrt[3]{-8}$ or Power[-8, 3^-1], Mathematica gives the ...
54
votes
4answers
7k views

Can I simplify an expression into form which uses my own definitions?

This seems like a simple thing to do, but I couldn't find anything relevant from Mathematica documentation. So suppose I have an expression: a*b/(a + a*Cos[a/b]) ...
50
votes
8answers
18k views

How to avoid returning a Null if there is no “else” condition in an If construct

I need to use If but with only one option that is if "a" then do "b", else do nothing. So I wrote If[a,b] but the problem is ...
27
votes
6answers
13k views

Replacing composite variables by a single variable

To replace a single variable by another variable, one can simply use the the replace all (/.) operator (e.g., ...
36
votes
5answers
39k views

Plotting Complex Quantity Functions

Trying to plot with complex quantities seems not to work properly in what I want to accomplish. I would like to know if there is a general rule/way of plotting when you have complex counterparts in ...
41
votes
3answers
2k views

Funny behaviour when plotting a polynomial of high degree and large coefficients

I am trying to plot a polynomial of degree $29$ on the domain $[0,1]$, with fairly large coefficients: ...
43
votes
4answers
8k views

Why does MatrixForm affect calculations?

This is a really newbie question, but it has me confused. Why does this code work without // MatrixForm and doesn't work with ...
169
votes
9answers
56k views

Elegant operations on matrix rows and columns

Question The Mathematica tutorial has a section 'Basic Matrix Operations', describing operations like transpose, inverse and determinant. These operations all work on entire matrices. I am missing a ...
23
votes
2answers
1k views

Ordering problem

Let's look at the following example. Ordering[{0, 20 Sqrt[5], 40 Sqrt[5], 20 Sqrt[5], 20 Sqrt[10]} // N] gives the right answer ...