# Questions tagged [conditional]

Questions about programming or mathematical constructs that enable verification, selection, or branching behavior when one or more criteria are determined to be True.

63 questions
Filter by
Sorted by
Tagged with
24k 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 ...
3k 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: ...
6k views

### 2D random walk within a bounded area

I want to simulate a random walk in two dimensions within a bounded area, such as a square or a circle. I am thinking of using an If statement to define a boundary. ...
1k views

### Quick way to use conditioned patterns when defining multi-argument function?

I have a simple function that is supposed to only accept numeric values (i.e. complex/real numbers and constant symbols e.g. Pi, E). $$f(a,b,c)=a+b+c$$ Edit: I should have chosen a less simple ...
1k views

### Simplifying conditional expressions using assumptions does not work

I have a conditional expression f[x_] := x /; x ∈ Reals This works fine for normal numbers and symbols, e.g. ...
327 views

### Set conditions at a permutation

I need to find all permutations of 3 elements from {a,b,c,d,e} with this condition: These must include element d maximum once, ...
16k views

### How to remove ConditionalExpression from output

I need define the function with parameter so I could directly generate a power series expansion. The problem is that in some cases ConditionalExpression appears in output. Here is my code: ...
20k views

### Add assumptions to Solve command

I want Mathematica to solve the following by assuming the part within the Log function, which is ...
255 views

### How to use Compile to generate an $n\times n$ array using $n$ vectors

Let's consider the following: ...
462 views

### How do I color Riemann integral rectangles using conditionals?

I'm building a function to visualize the Riemann integration process for any function using rectangles. Everything is fine, except that I need the color of the rectangles to change if they're under ...
1k views

### Generating Tuples with restrictions

I am interested in a certain subset of all tuples. Generating all with Tuples and then filtering is wasteful, and will "blow up" very quickly. For a concrete ...
3k views

### Generate "nice" random matrix

I don't frequent this community, so please give criticism if this is a poor question. I am trying to make a tool which generates a small (say, $4\times 4$) matrix with integer entries, which has a "...
3k views

### Simplifying nested If statements

Consider : list = {100,102,103,99,106,107,104,112} I want to consider, extract only the "big moves" of that time series. In this case the moves bigger then 5 ...
4k views

### How to restrict the domain of a function

I realize this question has been asked many times, but I am fairly new at Mathematica and the other answers are very complex, and certainly too complicated for this simple code I am trying to write. ...
356 views

### Why does pattern test not work in this case to restrict the function parameters?

I was looking at this Q&A about using pattern test (pattern_?test) vs pattern condition (pattern_/;cond) and came across ...
281 views

### How to condition arguments of a pure function?

I would like to exclude the point {x=0,y=0} in the function definition ...
309 views

### Recursive function, if and which statements

I am given this question: Let a function $T_n(x)$ be defined by: $$T_{n+1}(x) = \frac{1}{x} T_{n-1}(x) - \frac{2}{7} T_n(x),$$ where $T_0(x) = 1, T_1(x) = x$. I need to construct a recursive ...
127 views

### Faster use of Condition for a large array (see the example)

Here is the example/problem. I have a array of $n$ random number. n = 2000; p = RandomReal[{0, 9}, n]; I have to create a $n\times n$ sparse matrix with $(i,j)$...
262 views

### Join matrix based on conditions

Given the following matrix: ...
219 views

### PlotStyle based on If condition

So in the If[evecs==Re[evecs], I want to then change the colour in PlotStyle of the ...
100 views

### Create bold headings and rows in TableForm if x is prime

In the following table ...
37 views

### Mathematica Function Taxicab Numbers [duplicate]

I have spent days trying to compile this code and I cannot generate a list of taxicab numbers for the Hardy-Ramanujan Theory. Here is the module I wrote earlier: ...
78 views

### 3D-plot of a maximization of a definite integral

I'm applying the answer (If method) suggested by 'ThatGravityGuy' in this post in a more complicated case. Consider my objective function (pardon its formidable ...
24k views

### Multiple lines in an If statement [closed]

What I am wondering is how do you perform multiple lines when using the If statement. I know the following is not proper Mathematica code, but how would I do this in Mathematica? ...
1k views

### Difference between Piecewise, Which, If?

I have the impression that these functions have different evaluation rules. I cannot produce a minimal example right now, but in general, what are the differences between these functions? That is, ...
630 views

### How to split list into segments based on first element of sublist, and remove ineligible segments

I have a list that looks like this: ...
485 views

### Why does pattern test work only with pure functions?

Why is it that pattern test works only with pure functions? Cases[Range[0, 70], _?(Divisible[#, 7] &)] Cases[Range[0, 70], x_?(Divisible[x, 7])] I ...
512 views

### How to simplify block of multiple repetitive If statements?

I'm building a boardgame...game in Mathematica. I have the board state represented as a matrix. It's a two player game, and each player (let's call them A & B) only has one type of piece or '...
646 views

### How to select points from a table that are within some region

there, I encountered this problem while coding: I generate a table in the r-z plane of cylindrical coordinates: ...
232 views

### Multiple down-values with exactly the same lefthand side

I was working on an answer to this question, when I was sidetracked by what I bring up here. I wanted a function, which when given a string representing a binary number, would convert the string to a ...
667 views

### Can one compile the Switch function?

I am aware that one can compile Which, e.g.: ff = Compile[x, Which @@ {x < 0, 2, x >= 0, 3} ff[1.] ...
222 views

### Check if a symbolic matrix is hermitian

I have a symbolic matrix: Potential = SparseArray[{Band[{1, 1}] -> V0/2, Band[{2, 1}] -> V0/4, Band[{1, 2}] -> V0/4}, {2*max + 1, 2*max + 1 }] ...
1k views

### Creating a conditional table

I'm trying to create a conditional table. Let's say I want to have such result: {1,2,3,4,5,0,0,0,0,0}. The idea is to create a table of n elements (10 in a given example), but when one element takes ...
127 views

### Solving Piecewise Differential Equation

I am trying to simulate something using differential equations. However, the equations are piecewise. Here is my code: ...
925 views

### How to leave function unevaluated programmatically?

Is it possible to write a function in such manner, that it can be either evaluated or left unevaluated? This is a general question. Sample below is just a sample. No need to find solution for this ...
105 views

### Why does conditional NExpectation fail for a multivariate distribution?

To give an example for a multiparametric distribution let us take a binormal distribution: ...
163 views

### Modifying a list of matrices with conditional statement

I have a list of around 100 matrices, that looks like this ...
772 views

### Find Array Elements That Meet a Condition

I have an array of 5 numbers (say m). I want the following operation m=[-1,-3,-2,-5,-4] For (j=1,j==5,j++) if ...
51 views

### Plotting an integral where the integrand depends on the parameter values (If)

With my function $f(x)$ I would like to Plot3D $\int_a^b f(x) dx$ with the parameter values $a \in [0,1]$ and $b \in [1,3]$. The challenging part has to do with ...
1k views

### Double Sum Involving Condition

I would like to compute the dimensions of some small free nilpotent Lie algebras. However, I am totally new to this and I could not figure out how to write the double sum which gives the dimension of ...
950 views

### ContourPlot with certain contour values omitted

Suppose I want contour plot of $x^2-y^2$, for $x,y\in[0,1]$ (my actual function is more complicated). Over this interval, $x^2-y^2$ is sometimes positive and sometimes negative. Using ...
150 views

### What is the syntax to conditionally suppress plotting in version 9?

Bug introduced in 9.0 and fixed in 9.0.1 In Mathematica 7 it is very easy to conditionally suppress plotting of individual lines using If: ...
371 views

### How to use Assuming and If together?

I would like to compare variables t and u and print either Yes or ...
764 views

### How to avoid applying Cross to a single argument?

I am looking for the simplest way to avoid applying Cross to a single argument. ...
282 views

### Table doesn't replace inside conditionals (If, Which) [duplicate]

This: Table[If[cond, y], {y, 1, 3}] outputs this: {If[cond, y], If[cond, y], If[cond, y]} The ...
119 views

### Except[] with levelspec

I am trying to determine all the variables used in list. For This I use: DeleteDuplicates[Cases[l1,_Symbol,-1]] This is great except that ...
246 views

### Delay Evaluation of First Argument of ConditionalExpression until Second Argument Evaluated

A particular set of equations I am solving, sol = Solve[...] yields a lengthy List of ...
41 views

### Which condition inside a loop with unknown value in a condition

I have a Which condition inside a loop such as: ...