Questions about the use of built-in Mathematica functions, including pure functions.

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21
votes
1answer
510 views

Shorter syntax for Fold and FoldList?

I find it tedious to write out the following: a = {1, 2, 3, 4}; Fold[f, First @ a, Rest @ a] f[f[f[1, 2], 3], 4] It ...
4
votes
1answer
70 views

Split/unmerge merged cells in notebook file

I have merged cells in a Notebook file. Is there a way to split such a merged cell group back to single cells, in each of them being one command?
4
votes
0answers
80 views
0
votes
2answers
31 views

How to get Complement function working in a For loop? [closed]

I've been working on a piece of code that will delete small components from a nested uneven matrix (n pages, n rows, 3 columns), by deleting the pages with less than ~30 rows. However, I've notice ...
4
votes
2answers
114 views

Initializing several values of a function

How do I initialize several values of a function at once? Consider the function f[0] := 1; f[1] := 2; f[2] := 3; f[n_] := f[n] = f[n-1] + f[n-2] + f[n-3]; Is ...
0
votes
0answers
177 views
2
votes
1answer
182 views

Making Mathematica function files like in MATLAB

I'm a MATLAB user trying to get familiar with Mathematica. I have long Mathematica sheet that spits out some matrices at the end after much math. I want to run a loop over couple of different initial ...
0
votes
2answers
106 views

How to make a list of Plots of derivatives of a function?

I did that.. i don't see what i did wrong. How would you do this? I want to use it for ListAnimate. ...
1
vote
1answer
68 views

Apply solution rules to new functions as parameters [duplicate]

Update: I put an screenshot of how my code and problem look like at the end. Say that Mathematica solved a system of equations and got two answers {{a -> 3, b -> c, d -> 0}, {a -> -3, b -> 0, c -> ...
3
votes
1answer
201 views

Fixed-Point Numbers in Mathematica

I am working with a library that needs input in a Fixed Point notation. I’d like to figure out a way to convert the floating point results into fixed point representation. The fixed point length is ...
2
votes
2answers
191 views

Permanently rounding numbers/values to a given number of significant figures

I am searching for a simple way of rounding and setting an input to a desired number of significant figures. There are a vast number of posts that discuss similar problems, but none address this ...
0
votes
0answers
19 views

Protected Tags Error [duplicate]

While trying to run this piece of code: ...
2
votes
0answers
49 views

Problem with plotting a function that calls FindRoot

I am having difficulties in plotting the solution of FindRoot to solve 4 variables. I defined a function and then tried tp plot it, but got an error message ...
2
votes
0answers
39 views

Covariance matrix estimation when number of variables is larger than number of observations

It is well known that the sample covariance matrix estimator results in a singular matrix if the variables is larger than the number of observations. One solution is to apply shrinkage estimators. ...
1
vote
3answers
57 views

Controlling the evaluation of other arguments in pure functions [duplicate]

I have a piece of code where I would like to do the something like the following: ...
3
votes
1answer
80 views

Partial fraction expansion with complex numbers

$$\text{Apart}\left[\frac{1}{x^4+1}\right]$$ Does nothing. How can I get it to expand it. Sometimes it is useful.
1
vote
2answers
58 views

Using Apply on a function with multidimensional input

I have a user defined function which takes multidimensional input, e.g a function that takes two algebraic variables a and b as well as a matrix m and computes some rule function as: ...
3
votes
1answer
97 views

Smoothing a unit step function

I want to smooth a unit step function for use in NDSolve so this function is a smooth function of time (t). How can I do the ...
5
votes
1answer
150 views

Can Mathematica Operators be combined in a linear fashion for readability? [duplicate]

Here's a simple example. Suppose we want to find the off-diagonal matrix of m: m={{1,2},{3,4}} This can be solved fairly simply by extracting a list of the ...
2
votes
1answer
292 views

Smoothing a single rectangular pulse in NDSolve

Hello I am interested in smoothing out the sharp edges of a single rectangular wave centered at the origin. I am looking for a smooth function that looks almost exactly the same as the square wave ...
12
votes
1answer
280 views

How do I create a triangulated surface from points?

I have a set of points in a nx3 matrix and I would like to convert them into a surface, so that I may calculate its surface area. The function ListSurfacePlot3D creates the surface how I want it. ...
14
votes
1answer
154 views

How does Rescale[] handle infinities?

Rescale appears to be a simple function. It just does a simple linear $y = a x + b$ type rescaling of the values: ...
0
votes
1answer
61 views

Calculation Performance (slow Plotting)

I have a functions, which is an Integral. It is exaclty this function Zf[x_] := 2*I*NIntegrate[Exp[-y^2.0 + 2.0*I*y*x], {y, 0, Infinity}]; Later I need to plot a ...
2
votes
4answers
758 views

I need F(x,y) = xy (not x*y) e.g. x= 1, y =2 so F(x,y) = 12 [closed]

I just need F(x,y) that give me e.g. x= 1, y =2 so F(x,y) = 12 Is that possible. I tried Google but not able to find a ...
1
vote
1answer
37 views

How do I express an equality as a function of one of the equality's variable?

Say I have this equality: (-52271 - 200 x + 100 x^2 - 1058 y + 529 y^2)/52900 == 0 and I want the same equality, but expressed in a function of x, as in y(x). ...
-1
votes
1answer
55 views

List command separating multiplicative terms [closed]

I am trying to separate and store additive terms via the List command. For instance I want "AB+CD+XY" to be stored as {AB, CD, XY} This has worked well, but when there is only one term (only ...
6
votes
0answers
60 views

NotebookWrite a Cell with WholeCellGroupOpener option

Why NotebookWrite[ EvaluationNotebook[], Cell["ZZ", "Section", WholeCellGroupOpener -> True] ] produces: ...
1
vote
1answer
88 views

How many arguments does a function require, and how to use that in `Manipulate`

The goal is to vary the order parameters in wavelet transforms in the Manipulate environment. The various transformations have arguments of different rank. For ...
2
votes
2answers
91 views

How can I partially evaluate a function?

I have a multivariable function, from which I'd like to define a marginalization: f(a,b,c,d,...,z) ---> g(a,1,c,d,...,z) Generally, g will have fewer argument than f, possibly none (full ...
1
vote
1answer
84 views

Absolute uncertainty and error propagation with lists [closed]

I am trying to do some error propagation using mathematica. This is my second day using the program. I am trying to take the derivative of a numerical function that is made up of the following lists. ...
-1
votes
1answer
212 views

Some Problem with WhenEvent! [closed]

Anyone knows what's the problem with the following code and how can I fix it? I am not sure that I wrote the WhenEvent section correctly. By the way, I want to solve the equations and then plot y vs. ...
1
vote
2answers
47 views

Insert several rows and problem with Return

I wanted to write myself a function that makes it possible to Insert several rows into one list. ...
1
vote
1answer
39 views

How to find all gaps of a domain of a function with Mathematica 9?

I tried it liek this: My test-function: fuu[x_] := Expand[FullSimplify[1/x]] how i find the domain: ...
2
votes
3answers
132 views

Defining a 2-variable function over voronoi diagram

I am new to Mathematica & I am facing a problem as follows: I have created a Voronoi diagram and now I want to assign to each region, a value, i.e., I want to extend this Voronoi diagram to form a ...
0
votes
1answer
61 views

repeat calculate [closed]

I want to calculate the below program x[t+1].But I can only calculate t=0,1. please tell me how to calculate t = 0 to 10. ...
2
votes
1answer
77 views

What's the difference between functions and replacement?

I used to thought that calling a function is equal to applying a rule, i.e. applying a rule of f[x_]->sth. is equal to calling a function f with definition f[x_]:=sth. However, given ...
1
vote
0answers
68 views

How to Implement a “Function Object” suitable for NDSolve and Finite Element Method?

I have a bunch of methods that shoud return an expression that behave like a function, i.e. an expression that, when supplied with suitable arguments, evaluate to something. A simple ...
1
vote
3answers
88 views

How to replace element of list by index

I'd simply like to replace the value x at index [[j,i]] in a two dimensional table with the value ...
2
votes
1answer
57 views

How to run a function over an increasing set of integers to find a fixed point

I have a function which runs a sum from -integer to integer based on some data, something like, schematically ...
1
vote
1answer
58 views

How to TakeWhile not zero of functions?

fuu[x_]:= 2 - x^3 + x^7 This works: TakeWhile[{5, 4, 3, 2, 2, 1, 0, 0, 0, 0}, # != 0 &] (*{5, 4, 3, 2, 2, 1}*) This ...
0
votes
0answers
15 views

Is there a list of function shorthand notations, shortcuts, and other various symbols somewhere? [duplicate]

For example how you can use // to apply some functions like Simplify instead of enclosing the argument in square brackets. Or ...
1
vote
1answer
148 views

In there a way to derive the inverse value of CDF format MultinormalDistribution?

Is there a way to produce the inverse value of multinormal distribution function in CDF format with 0.05 significance level? I found the function called ...
15
votes
0answers
221 views

Is FullGraphics an abandoned function? Is there an alternative?

FullGraphics hasn't worked entirely for a long time and the situation appears to be getting worse instead of better. In Mathematica 10.0 and 10.1 a simple usage ...
3
votes
1answer
137 views

What is the relationship between Thread and MapThread

I hope this is not a silly question, since there are plenty of questions on Thread and MapThread. However, I still cannot quite ...
2
votes
1answer
403 views

Matrix exponential MatrixExp[] vs Sum[MatrixPower[]] doesn't match?

I might be an idiot, but I cannot get the manual expansion of $e^{At}$ to match the MatrixExp[A t] result. For example, I have the following: ...
2
votes
1answer
38 views

Strange behavior when defining a symbol/function pointwise

I am well aware of the fact that floating point number have finite precision, so one needs to be careful when comparing them. Still, I find it disturbing/surprising that the following input into ...
1
vote
1answer
41 views

Finding parameters for which a function/symbol is defined

Suppose I have a symbol/function defined pointwise like in f[1, 5] = 3 f[3] = 7 f[2, 3.4] = 8 By executing ?f I can see the ...
0
votes
1answer
73 views

What is a good way to check what kind of a function a function is?

i want a module or function or switch or If (whatever works), what asks if a function is an e function or a polynomial(a hole number one or fractorial), a exponential function, a logarithm function ...
7
votes
4answers
241 views

How do I invoke the default complexity function?

Documentation on ComplexityFunction says: With the default setting ComplexityFunction->Automatic, forms are ranked ...
4
votes
0answers
83 views

Unexpected behavior from Indexed

I was going to include Indexed in this answer, thinking that it operated much as a List-only ...