# Questions tagged [equation]

A statement that the values of two expressions are equal indicated by the sign = .

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### What is the formal regression equation used by lm.cluster in R?

When using lm.cluster, I have three fixed effects variables (which have different levels), and 1-3 'explanatory' variables (in one case I have 1, and in another case I have 3). What is the formal ...

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**3**answers

44 views

### Display the item nearest to current time

I have a list of dates/times items in PHP array that are formatted like this:
2019-03-19 00:00:00
2019-03-19 02:30:00
2019-03-19 05:00:00
2019-03-19 14:30:00
2019-03-19 23:59:59
etc.
I'm sure this ...

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**2**answers

49 views

### Finding the odd point in a dataset without using loops

I am given a set of points (p1,q1) (p2,q2) ... (p20,q20) which satisfy the function q = 1/(ap + b)^2 except that one of these does not satisfy the given relation. The values of a and b are not given ...

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**1**answer

49 views

### Calculate variables from 6 non-linear equations with 6 unknowns in R

Looking to calculate a,b,c,d,e,f (6 variables) from 6 non-linear equations:
The following is my code
library('BB')
library('nleqslv')
y <- rep(NA,6)
params <- function (x) {
a <- x[1]
b &...

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**0**answers

43 views

### Is there a way to change a string equation into a sympy equation?

When the user enters a value from a dropdown menu in Tkinter (e.g. frequency), all the equations containing the parameter will be displayed. I have managed to find all the equations when a value is ...

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19 views

### More advanced mathematic typesetting using groff and eqn?

I've been learning Groff and eqn for document typesetting - I'm a physics and mathematics student, so a lot of my documents require semi-complex mathematical formatting.
Generally, I'm using eqn for ...

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**0**answers

29 views

### How to add regression equation and r^2 to plot [duplicate]

I have tried countless other attempts at getting the regression equation and r^2 onto my graph. Here is the code and graph it produces...
temp_var <- predict(model1, interval="prediction")
new_df &...

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**0**answers

40 views

### Equations with boundary condition in python

I want solve an equation with boundary coundition
Here is first equation :
d/dx (k * dT/dx) = 0
k=1000
After 2 integral we have this equation :
T = (C1 / k) x + C2
And the boundary conditions are ...

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15 views

### How to solve overdetermined quadratic system in Circle Packing

I'm working on a program where I have to satisfy an overdetermined system of non-linear equations.
Basically, the program will add points dinamically, and every new point must be added where it ...

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**2**answers

95 views

### How to solve a linear system of a square matrix in C++ when the matrix has no LU-Decomposition?

I have been trying to develop a program to solve a system Ax=b for a square matrix A using LU-Decomposition. However, I realized that this decomposition does not always exist (one way to tell is if a ...

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10 views

### Equation to calculate position in grid

I have this pattern and am not sure exactly how to turn it into an optimized equation for mapping to a block (0000, 1111, or 2222).
1111 0000 1111 0000 2222 2222 2222 2222
0000 1111 0000 1111 2222 ...

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**0**answers

28 views

### Calculating Loss Ratio when Premium is Negative

I've been looking around the Interwebz and have been unable to satisfactorily answer this question. I've looked at documentation from actuaries, insurance companies, and a number of other sources, ...

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**0**answers

8 views

### asciimath: Equation numbers

How can I get equation numbers added to asciimath:[] expression?
That is, how can I get the '(5)' in the formula such as
E = m c^2 (5)
Is there a method to refer to equation ...

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**0**answers

31 views

### NameError: name 'x' is not defined for an equation program

I am trying to program an iterative equation that will iterate the equation based on the number of times a user specifies. I have the following code:
import matplotlib.pyplot as plt
import numpy as ...

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**4**answers

37 views

### Python3 - solve math equations that are in string format [duplicate]

Is there a way to solve math equations that are in string format?
For example, I have
x = 2
y = 3
equations_str = ('x+y', 'x-y')
and I want a function that will give
results = (5, -1)
I want to ...

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**0**answers

24 views

### Equation of line bending into a 3D knot

I want to animate a line bending into a knot for a presentation. I cannot figure out what equations I need to model. I know the equation of knot, but is it possible to know what equation the particles ...

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**2**answers

37 views

### Python: read a variable from list of a file in order to calculate equation

I have to calculate different equation (we assume 3 reactions). Each one uses a different variable and I have to read this variable from a file list.txt.
So my idea is:
f = open('list.txt')
lines = f....

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**0**answers

13 views

### an error while multiplying two symbolic functions in system differential equation

Iam running this code in matlab to solve a system of two diff equations.
Every thing works until I add in "eq2" a multiplication by t, and then I got an error
Warning: Explicit solution could not be ...

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**3**answers

48 views

### Iteration for x value in equation

I've been set a task to iteratively calculate the value of x of the given formula : x3 - 3x + 4 = 0** using trial and error.
The code will first plug in -1.5 as its first guess and then work up or ...

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11 views

### Describing long numbers in a short way

Imagine we have a number with N digits. N can be 100, 200, 1000,000, etc. Let's suppose we have a 100,000-digit number.
Such a number can start with 0000000..................00001 (with 100,000 ...

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29 views

### Solve constrained equation with 12 variables

I am struggling with something that should be a simple task. I want to solve this equation to find all the possible solutions (for Xi, i=1...12).
Y = a*X1 + b*X2 + .... + z*X12
(I have 98 fixed ...

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19 views

### How to use the Levenberg-Marquardt algorithm to fitting data and get the first derivative in Matlab?

I'm implementing the Levenberg-Marquardt algorithm in matlab to minimize a set of data resulting from a black-box equation.
My question is how to calculate the jacobian matrix?

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**2**answers

80 views

### Parse equation to list of tuples in Python

I want to parse equations and get a list of tuples.
For example, when I enter
2x = 4+3y,
I want to get
[('', '2', 'x', '='), ('','4','',''), ('+','3','y','')]
This is my regex so far:
([+-]*)(...

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votes

**0**answers

28 views

### Solve equation saved within a column

I have a data frame in R with a series of equations as a column and the variables to be used in the equation in additional columns:
data.frame (equation = c('2+d','2+4+d*h','(5*d^h)/100'),
...

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**0**answers

32 views

### Algorithm to solve diophantine equation

I'm trying to develop an algorithm for finding positive integer solutions with an upper bound of a diophantine equations like this:
a^3 + b^3 + c^3 = d^3
For example:
3^3 + 4^3 + 5^3 = 6^3
I want ...

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votes

**1**answer

21 views

### Plot solutions of bivariate polynomial equation [closed]

How can I plot the solutions of this equation in R?
(x²+y²-1)³=x²y³

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vote

**1**answer

51 views

### Correlation coefficient for three variables in r

For three n-dimensional non-zero-variance variables a, b, and c, n > 2, if
r(ab), r(bc), and r(ac) are Pearson’s correlation coefficients between a and b, between b and c, and between a and c, ...

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**1**answer

34 views

### How to return all whole positive values for a+b = c+d while a,b,c, and d are not equal to each other?

Is there a way I can find all the values between certain parameter such as (1,10) that satisfy a+b = c+d while a,b,c, and d are not equal to each other.
var a;
var b;
var c;
var d;
function ...

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vote

**0**answers

43 views

### Writing a correlation equation into R

I am trying to turn this equation into r-code to apply to a dataset. I made an example data set:
a <- c(4, 6, 2, 5)
b <- c(8, 1, 3, 7)
c <- c(6, 3, 1, 3)
d <- c(7, 5, 7, 5)
data <- ...

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**2**answers

51 views

### C++ results with formula not matching specifying value

Why do the following not equal each other?
0.37024025
and
(sqrt(2)*M_PI/3)*(1/4)
I see significant divergence in my solution, but all I did was place a number with the formula behind it.

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votes

**1**answer

37 views

### OpenCV solve returning constant value for arbitrary system?

I initialize a 4x4 matrix to the identity matrix. Then I initialize a 4x1 vector B with random values. And I want OpenCV to solve the system Ax = B.
Since A is the identity, my expectation is that x =...

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**1**answer

21 views

### variable extraction from equation in MATLAB

I'm trying to solve for T4 in the following equation in MATLAB, I have all other variables defined and I need to extract T4 from equation 1. Is there a quick way to do this rather than manually ...

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22 views

### What is the error with equating a value in an ArrayList to a String? **The ArrayList is type String** [duplicate]

I am trying to create a quiz type thing for Math 30-1. I just started and have already run into an issue that I have never had before, (or can't remember how to fix it). Below is a piece of the code ...

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votes

**1**answer

26 views

### Python - optimizing math equation for a simple guessing game score calc

I'm trying to create a equation similar to a messy block of code I've made, to calculate the score based on the amount of guesses a player took in a guessing game.
The player has 10 tries. For every ...

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votes

**2**answers

51 views

### Nesting if statements no strings

I am doing a Palindrome number sequence. I've got the math set up, but I'm having trouble nesting my if statements only showing one answer.
I've attempted to remove the 'if' from the 'else if' but ...

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vote

**2**answers

112 views

### Plotting a circle equations in Julia

I have a problem to plot a circle equation in Julia.
I'm trying to plot these two equations:
2y^2 + x^2 = 2
(x-1)^2 + (y-1/2)^2 = 1/4
At this time, the only solution i found is using ...

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votes

**1**answer

67 views

### Using scipy solve_ivp for equation with initial conditions

I am having a hard time getting used to scipy's solve_ivp. So let's say we have an ordinary linear differential equation of second order, spring for example (y'' = -k**2*y). Conditions are when the ...

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vote

**3**answers

48 views

### Code Double Equation Error for User Input Problem

My first assignment is to develop a code that allows the user to input data for the distance in miles they wish to travel, the fuel efficiency, and the cost of gas. Then create a code in order to ...

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12 views

### using an array in an equation in python

So I am trying to loop through an array in an equation and I can't seem to find my error. lamda[wav] is where I need to pull the number in the lamda array. The code is as follows.
import math
c = ...

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32 views

### Creating equation using matlab

I'm trying to perform blind source separation (BSS) on bioacoustic signals using DUET algorithm. I have 4 individual sources. Can anyone help me to write Matlab codes if I want to artificially mix the ...

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vote

**2**answers

92 views

### Find (x,y) solutions to equation

The program receives a positive number k from the user and should check how many solutions there are to the equation
3*x+5*y=k
In case of many solutions the function takes the greater absolute value ...

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**0**answers

18 views

### Stringing together a sentence from data that includes dates

I have a question regarding this topic;
I'm also looking to put together a string of data into a sentence using excel, and the issue I'm running into involves dates.
="ISP Annual was completed on "&...

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votes

**1**answer

54 views

### how to find satistics of the fitted parameter of an equation [closed]

For instance: a, b, c and n are the three constants, which are required to be calculated by using data fitting method in a particular equation.
How can I calculate the statistics (mean, standard ...

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vote

**1**answer

31 views

### How to make a function in python that takes a product and re substitutes in equation to get a solution

I'm trying to make a function in Python 3 that takes an initial value, plugs it into an equation, takes that solution, and iterates the process as many times as specified as a parameter of a function. ...

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**1**answer

60 views

### Python - Finding the linear equation of a line in a image

I am using Python v2.7 for this work.
As an input i have a relatively white image with a clear black line on it. The line is always linear, no polynomial of second or above order. The line can be ...

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**1**answer

66 views

### looping a mathematic equation [closed]

so i'm trying to make a cashier like program that keep add up depend on how much the user buy the product, but my program wont add the value but it keep replacing it
Class:
public class Class {
...

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**1**answer

68 views

### Solving Ax = b , CUDA vs Matlab

I've done the following test on Matlab:
n = 10000;
A = rand(n,n);
b = rand(n, 1);
tic
y = A\b;
toc
On my Intel i7 gen 5 machine (12 cores) the result is ~ 5 seconds.
Then, I've trying to do the ...

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**1**answer

693 views

### Convert an equation to Python

I have several equations and need to convert it into Python. The problem is that I tried to plot a graph according to the equation. However, the graph that I get is not the same as the original one.
...

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**1**answer

75 views

### how can I use sympy to solve system of equations with constraint conditions

the example like this:
x1 + x2 + x3 + x4 = 1
x3 + x4 = 1
x4 + x5 = 1
x4 + x5 + x6 = 2
x1,x2,x3,x4,x5,x6 belong to this set {0, 1}
so you see, it's a linear system of equations.
...

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votes

**1**answer

57 views

### How to covert this specific equation to matlab code [closed]

How to represent this equation to matlab code