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# 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.

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### Make a list of the first 100 primes, keeping only ones whose last digit is less than 3

This is a question from an "Elementary Introduction to the Wolfram Language" Section 28: Tests and Conditionals. We are asked to "Make a list of the first 100 primes, keeping only ones ...
77 views

### Condition inside pure function

Why condition /; not work inside pure function? Suppose we have: ...
100 views

### Compute the area of the union of the intersections of two conditions

I have four conditions over the two-dimensional domain $x,y\in[a,b]$. I want to use NIntegrate to compute the area of the union of the intersection of the two ...
40 views

### Optimization of conditions applying

Let we have some data generator, e.g. lazy tuples or permutations. I need to select data by some conditions cond1, cond2, …, up to 5-6 conditions. All of them need ...
1 vote
360 views

### Parallelize a "For" cycle

I'm trying to parallelize a simple routine inside a "for" loop. Essentially, I need to compute the roots of a function $f(x)$ that depends on the discrete parameters $d$ and $R_0$. However, ...
1 vote
57 views

### Weird behavior of Which with lists [closed]

To demonstrate my problem, let's create a little function: ...
129 views

### Convert list of conditional expressions to list

I have a long list of items of the form ...
55 views

### Efficient and compact replacement for Association in the following case

Consider the following association: ...
74 views

### How to minimize computational time in an if condition?

I have a code as below: ...
297 views

### Why does Select not work here?

Why does this not work? It returns empty while I expect the first two elements are selected. ...
142 views

### Generate all adjacency matrices of size $n=4$ s.t. $a_{ij}\neq a_{ij}$ and $a_{ii}==0$

I want to generate a list of adjacency matrices of size $n=4$ s.t. The diagonal is zero: $a_{ii}=0$ for all $i\in\lbrace 1,2,...,n\rbrace$ There are no 2-cyles, i.e. if $a_{ij}==1$, then $a_{ji}==0$ ...
116 views

### How to discard the repeating elements of a list [closed]

Lets say there is a random list of expressions : a={Sin[x], Sin[3 x], Sin[4 x], Sin[x], Sin[4 x], Sin[x], Sin [5 x], Sin[3 x], Sin[5 x]} Plot[{a}, {x, 0, 2 Pi}] ...
1 vote
89 views

### Selecting only one out of many: Differential equation

I have the following code: ...
112 views

### Selecting the specific values from a table and saving in a table:

I have the following code: ...
43 views

### Preventing Evaluation of Body of Manipulate

Overall, I am looking for a way to prevent the evaluation of the body of Manipulate until the controls meet a certain condition. For example, consider the following....
98 views

### The fastest and most scalable way to write a nested loop

The problem is to find the weights {w1,w2,w3,w4} that satisfy the condition. Which is the fastest and most scalable way (e.g. for 10000 weights) to write this ...
152 views

### How to select elements from a list of pairs based on first element belonging to a different list?

This is my very first question and I really appreciate this ability and thankful the community. I have two lists and need to select only those pairs from the first list, first element of which is ...
93 views

### Is there any alternative for conditional plot that gives a more precise result in a shorter time?

I have the given function $Func$ and want to have a plot of those domains where $-3\leq Func\leq 3$ in precise details. I am using ...
68 views

### How to plot multiple functions with conditions that assign values of some of them to be greater than the others?

i am trying to plot multiple functions in mathematica but i would like to do this in such a way that the values of two of my functions are always greater than the other two. my functions are: ...
79 views

### How to speedup comparison in the following example?

I have the following problem: I would like to generate random values of some variable $z$ obeying some distribution, but simultaneously within the interval zmin<...
181 views

### Creating a cycle with conditions

I would like to arrange a gift exchange between 5 people, Alice, Bob, Carl, Danny, and Ellen, and I would like the gifts to be passed in a randomly created cycle (B->C->A->D->E->B), for ...
84 views

### Removing "spikes" in data

Imagine I have a data set which gives me the following ListLinePlot Is it possible to define a function over the data set that removes the "spikes" ...
79 views

### Check the existence of roots based on parameters

I have a function which has one variable $r$ and two parameters $M,\lambda$. Whether or not the function has roots, depend on the parameters $M,\lambda$. I want to obtain a parameter space such that ...
81 views

1 vote
71 views

### Table mix with If function [closed]

Anyone could explain to me which problem is? after running the function "Table" combining with "If" as below, but the result is not a value instead. ...
117 views

### Unexpected behaviour of Condition with Cases/MatchQ?

When using the unsorted version of Complement in this question I met the following unexpected result, ...
835 views

### How to generate a list of random numbers with conditional statements

I want to generate a list of numbers with certain conditions. Eg. First I generated 10 random numbers between 1 and 20. M1= RandomReal[{1,20},10] Now I want to ...
93 views

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1 vote
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### Plotting a conditional expression

I'm trying to plot the feasible region of a maximization problem with PlotRegion3D. This region is the intersection of two constraints and I'd like to plot also the ...
213 views

### Modify list elements if last two entries are equal

Suppose I have a list as follows {{1, 1, 1, 1, 1, 3}, {1, 1, 3, 4, 1, 1}} and I want to check the last two coordinates are equal or not. If that is the case then I ...
76 views

### Select with simplification does not work

Given a list, I want to find all elements that have positive imaginary part. For example, if $y,z\in\mathbb R$ and $a>0$ and the list is $\{ ia+y, -ia+z\}$, then the result should be $\{ia+y\}$. ...
82 views

### Simplifying conditional expression

I have an expression of the form ConditionalExpression[I a + y1, {True, True, True, True}] as a result of some computation. (The expected answer is just ...
1 vote
77 views

### How to use an "otherwise" clause in Which

I want to classify a set of vectors according to the number and position of zeroes they contain. The components of the vectors are non-negative. I'm using ...
1 vote
112 views

### Conditional mathematical expression [closed]

I want to produce A, B, C, D and E values between 0 and 2*pi with two conditions: A!=B!=C!=D!=E And (C,D,E)!=n*pi/2 n is an ...
1 vote
92 views

### Using Loop to find a specific Energy

I am given a Hamiltonian: ...
99 views

### How to find that this be always real number

I don't know how to find out this is be real number for l[y]? ...
89 views

### If or Piecewise dependent coefficients in NDSolveValue

This: but the following (placing the partials inside the If) does not. Any suggestions?
215 views

### Creating a list of conditions

I am trying to create a list of conditions using Table[] in the following way: ...