Questions tagged [expression-test]

Questions about Mathematica's predicate functions.

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40 views

How can I show that the equation holds?

Suppose we have the following data: $ r=\frac{vk}{h^2}$ $u[i,j]$ is a function of two variables with $i,j$ integers. $\frac{u[i,j+1]-u[i,j]}{k}=v\frac{u[i+1,j]-2u[i,j]+u[i-1,j]}{h^2}$ Then I would ...
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1answer
60 views

How to test if $ⅈ$ is in an expression?

From this answer https://mathematica.stackexchange.com/a/9773/68791 and according to the documentation: FreeQ[list,form] test whether form occurs nowhere in ...
5
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2answers
249 views

How do I check if proportion of values in list are mostly positive?

I'd like to return a a boolean variable that tells me whether numbers in a list are mostly positive. For example: a = {3,2,3,4,-1,-2,-5,3} There are 5 ...
7
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4answers
628 views

how to write a condition for all elements of a list

I have a list a={no,no,no,no}; now I can want to an If so that if all elements of the above list are "yes" it does something ...
1
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1answer
56 views

TrueQ returning False on true, non-numerical statement

I'm trying to test the following logical statement: state = {{1,1,1}}; Or[state != 0, state != Null] but it's returning False ...
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2answers
138 views

Specifying that function argument is positive

Struggling with something basic. Suppose when defining f[x_] the outcome depends on Sign[x]. When calling this function, how do I tell Mathematica the sign of the argument? My attempt: ...
0
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2answers
59 views

Test if function of multiple variables is positive or negative given variable constraints

I have a function of multiple variables (5 to be exact). I would like to know if this function is positive or negative given certain constraints on each of the 5 variables. Here is a simplified ...
1
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1answer
47 views

How does one test whether or not an integration has succeeded?

This must be a very simple matter--but how to address it eludes me at the moment. I have a series of integrands--and want to flag whether the symbolic integation has succeeded or not (in order to ...
3
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1answer
83 views

How to prove a numerical identity?

Let be a function power function f[s_, r_] := Piecewise[{{s^r, s >= 0}, {0, True}}]; And its convolution ...
0
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1answer
36 views

Testing which expression is greater

I have two expressions: expr1 = e^2/(8 + 4*e + e^2) and expr2 = (d^2 - 2*d*e + e^2)/(8 + d^2 - 2*d*2 - 2*d*e + 4*e + e^2) ...
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4answers
848 views

How to check is there any negative term in a large list?

I want to check if a data set of size $10^{10}$ contains any non-positive elements. Positive[Name of dataset] returns a list of ...
14
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1answer
150 views

Why is IsomorphicGraphQ so very slow (in this instance)

Bug introduced in 10.0 or earlier and persisting through 12.0.0 Can someone explain why the following code does not complete within a reasonable time? ...
8
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1answer
295 views

Is there a defined priority for pattern matching?

If you define a function g, like so: g[x_?EvenQ] := "even" g[x_?NumberQ] := "number" why will Mathematica always return ...
3
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3answers
89 views

How to check expression depends on symbol in a particular way

Consider these two expressions: expr1 = a d g[X, c]^2 + e g[X, f] + 3 expr2 = a d g[X, c]^2 + e X + 3 How do I check whether these expressions depend on ...
23
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1answer
298 views

Which second arguments is VectorQ/MatrixQ/ArrayQ optimized for?

VectorQ and similar functions (MatrixQ, ArrayQ) treat certain second arguments specially. ...
2
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1answer
38 views

Symbolic variable for If argument [duplicate]

i want to realize an if in this way : var=expression; If[var==0, Print[Hello]]; If[var!=0, Print[Hey]]; The system doesn't know if ...
11
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2answers
369 views

About shorthand notation for conditional pattern (Paul Wellin “Essentials of Programming in Mathematica”)

I am reading Paul Wellin's "Essentials of Programming in Mathematica". Mr. Wellin wrote the following in his book: There is a convenient shorthand notation for conditional patterns that is ...
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0answers
15 views

I want to extract coefficients of a linear formula. But my code didn't work [duplicate]

I want to extract coefficients of a linear formula and I wrote the following function. But it didn't work. ...
0
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0answers
44 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 ...
22
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2answers
1k views

Why no RationalQ or RealQ?

Interesting pattern came up as I go through the homework replies of my students. Why is there no RationalQ or RealQ? We have <...
0
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2answers
109 views

Create my own `PrimeQ` function [closed]

I want to create my own functions, for example: Functions like IntegerQ,EvenQ and OddQ. My ...
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0answers
42 views

How to test consistency of two assertions without hacking

Suppose I have a set of assumptions assum = x ∈ Reals && y ∈ Reals and I want to test an assertion like ...
0
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1answer
82 views

TrueQ returns False [closed]

I have coefficient of some expansion: Workingexpansion = tau/n - (A tau^2)/(27 n^3) - (B tau^3)/(5832 n^5); CoefficientList[Workingexpansion, tau][[2]] ...
0
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1answer
88 views

Trying to generate random even number

I am trying to generate a random even number, and then try to write the list of primes that are composing it as Goldbach conjecture says. It's just a test to learn how to use mathematica, so I would ...
5
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0answers
58 views

Testing for membership with Bags?

Is there a faster way to test for membership in an Internal`Bag other than unpacking the whole thing like this? ...
2
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2answers
105 views

How to tell whether a character is a letter-like form

Is there any way to programmatically tell whether a given character is a letter or letter-like form (see this reference page for what I mean)? One idea I had was to use ...
0
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0answers
59 views

How to check if all the entries in columns of a matrix are equal?

Assume we have the following matrix/tensor. How can I test if the column has the same element? 4-6 and 8-9 columns has the same element. $ \left( \begin{array}{cccccccccc} \{2,3\} & \{2,3\} &...
1
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2answers
54 views

Make two expressions look alike OR check that they are the same

I would like to compare my Mathematica calulations with the results from a paper. I get: ...
0
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1answer
70 views

If ValueQ is buggy, what alternative is there?

The function ValueQ has been irritating me for a while. I can't find its use for anything. Inspect the following: ...
2
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1answer
400 views

problem with testing if two expressions are equal

I have a small problem: I have two expressions: a = (ia*l^3*p0)/(12*ia*l + 6*i*la) b = p0*l^2/(12*(1 + 0.5*i/ia*la/l)) Obviously, they are equal. Just take ...
14
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2answers
1k views

Checking if a word exists

Probably the simplest way to check a word if it exists is to use DictionaryWordQ[] DictionaryWordQ["color"] True But it ...
4
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2answers
356 views

Check if number is irrational/transcendental

Mathematica provides functions to test whether a number is an integer, even or odd, prime, rational, real or complex. However, I could not find any explicit way to determine whether a number is ...
1
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0answers
114 views

Want to know more about _?MatrixQ [closed]

User, @AndrzejKozlowski has uploaded a number of interesting demonstrations to the Wolfram Demonstration Project. I have a particular interest these days in his Pricing a Bermudan Option with the ...
0
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0answers
75 views

PolynomialQ always yields True?

I have a question about the PolynomialQ function in Mathematica. I have the polynomial (this is the Chebyshev's polynomial of the first kind) $$B=\frac{1}{2} ([x - \sqrt{(-1 + x^2)}]^n + [x + \sqrt{[-...
17
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7answers
1k views

How to check if a vector is an eigenvector of a matrix using mathematica?

Here is a vector $$\begin{pmatrix}i\\7i\\-2\end{pmatrix}$$ Here is a matrix $$\begin{pmatrix}2& i&0\\-i&1&1\\0 &1&0\end{pmatrix}$$ Is there a simple way to determine ...
1
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0answers
59 views

Speed up for SequencePredictorFunction?

From Google Dive: SequencePredictorFunction is here, along with my test data. From pastbin: prediction function and data is here. Using the ...
9
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1answer
200 views

1 is not the SameQ as Null, but why might 1 be Equal to Null?

The command SameQ[1, Null] returns False which is what I would expect, but the command ...
10
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5answers
761 views

Test if a list is a constant integer multiple of another list

I have a list of lists, and I want to eliminate all the lists that are constant integer multiples of another list. My initial approach was to divide the lists using nested tables. ...
2
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1answer
53 views

compare some functions

Assume that I have three function: sum1[n_] := Sum[Cos[k/n], {k, 0, n}] sum2[n_] := Sum[Sin[k/n], {k, 0, 2n}] sum3[n_] := Sum[Cos[k + 1/2n], {k, 0, 2n - 1}] For ...
1
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2answers
50 views

Simplifying tests on a random set

I would like to simplify: ...
1
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1answer
141 views

Simplify nested If into a loop

I would like to simplify a set of tests (meant to be applied on a random set of parameters), written for now as nested If: ...
6
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1answer
91 views

TagSet for symbol inside NumericQ behaves differently than in other fooQ functions

I am trying to define some symbols as being numeric by using TagSet and encountered the following different behaviors between NumericQ and e.g. ...
6
votes
2answers
3k views

Difference between != and =!=

I (think I) understand the difference between == (semantic) and === (syntactic). So when comparing != and =!= I was expecting a similar difference. So can anyone explain why the third line in this ...
4
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2answers
102 views

Condition syntax: “when equal to any of”

I am trying to write a condition clause for a certain expression. I need to pick out the following cases: Mod[x*y, 10] == 8, or Mod[x*y, 10] == 3, or Mod[x*y, 10] == 7. I need to repeat ...
3
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2answers
186 views

Test if two or more elements are in a list

I have a list of two-element lists {{a,b},{c,d},{x,y}} I can use MemberQ to test if one of these lists is present, for example ...
5
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2answers
177 views

RegionMember with geographical data

I'm trying to be able to calculate whether a coordinate is within a census tract. As an example, here's a particular census tract in Chicago defined as a set of polygon vertices: ...
5
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1answer
153 views

How to judge if two Dataset are equal

I don's sure this is a bug or not.Suppose I have a dataset ...
5
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1answer
117 views

PrimitiveMatrixQ?

Is there a simple way to test in Mathematica whether a non-negative square matrix $A$ is primitive? Primitive means that for some positive integer power $k$, all entries of $A^k$ (matrix power) are ...
3
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2answers
99 views

FullSimplify yields different output with exact and decimal input

I'm trying to define a predicate function to identify if the expression is a geometric sequence. This is the function I came up with so far: ...
2
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1answer
112 views

Are UnsamQ and Not[SameQ] the same function? [closed]

Why are the following functions a[x___] := If[ UnsameQ[x, Null], 1, 2, 3] b[x___] := If[ Not[SameQ[x, Null]], 1, 2, 3] different? For example ...