A mathematical model is a description of a system using mathematical concepts and language. The process of developing a mathematical model is termed mathematical modelling.
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1answer
53 views
Could you help me to find a model for this curve?
I am very bad in mathematics and I'm not able to find by myself the model corresponding to this kind of curve.
I wish to have a quick growth at the beginning, then it should increase slowly for a ...
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1answer
37 views
How to solve these simultaneous equations:
$1 = 1/2y - bx,$
$1 = 1/2x - ay$
I need x,y it in terms of constants, but I can't figure it out!
3
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1answer
55 views
Iterative model fitting
I have a sequence of points $\{(x_k,y_k,z_k)\}$ and I need to fit some $2D$ model $P(x,y)$ that approximates $z$ in some sense.
The $z_k$$'s$ are noisy samples of some $2D$ function $z_k = f(x,y) + ...
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1answer
98 views
Actuarial / Modelling question - difference between RUN date and VAL date
My understanding is that RUN date is the date you do the RUN (eg in prophet / moses / igloo / whatever, the date on which you performed the calculations)
Whereas VALuation date is the initial 'as at' ...
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0answers
52 views
Should I get the absolute value of the result of the inverse discrete fourier transform？
The result of equation 36 can be positive and negative.And if I don't get the absolute value of it,the ocean surface tend to be very regular.But according to the paper,the author never get the ...
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1answer
158 views
Complex results in inverse Fourier transform for simulating ocean water
I don't understand the equation37 in simulate ocean water by Jerry Tessendorf.The result is all complex number, how to be the slope.Even if I compute the magnitude of it，the result is just positive ...
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0answers
20 views
Model to reward adaptative communication
I'm currently working in different simulations focused on the study of artificial evolution of communications in robots, and I have stumbled against the problem of its mathematic formulation.
The ...
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0answers
45 views
Approximation of the graph - sigmoid
I have the following graph showing characteristics of different vectors , belonging to the same image. Is there any way to transform them , so that they are the same. As far as I see, there is a ...
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3answers
448 views
Cat Dog problem using integration
Consider this equation :
$$\sqrt{\left( \frac{dy\cdot u\,dt}{L}\right)^2+(dy)^2}=v\,dt,$$
where $t$ varies from $0$ to $T$ , and $y$ varies from $0$ to $L$.
Now how to proceed ?
This equation ...
3
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0answers
26 views
Regression model for a shearing process
30 Widgets are randomly assigned to a shearing process.
There are 3 such processes, each getting 10 widgets.
The lengths of each widget are recorded before undergoing the shearing.
The amount that ...
3
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0answers
60 views
How to model bending, folding of 2D figures?
2D shape can be folded in various ways. For example, trapezoid can have its sides (with the acute angles) folded, so that it will effectively become rectangle – with the difference, that part of the ...
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1answer
73 views
Calculating metabolism [closed]
I'm developing a calculator that calculates how much calories you burn per minute.
This formula is what I have so far:
...
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0answers
39 views
Best way to statistically compare two polynomial models?
I'm working on modeling and comparing data sets, and I need a good way to see if there is a significant difference between the data from the 2 models. An example of the models are here.
I initially ...
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0answers
74 views
Considering the predator prey model to find the range of values to be a spiral
I have the following problem:
Consider the predator-prey model: $$\frac{du}{dt}=u(1-\alpha(u)-v), \frac{dv}{dt}=\rho(-1-\alpha(v)+u),$$
where $\rho$ and $\alpha$ are positive parameters with ...
162
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16answers
6k views
Optimizing response times of an ambulance corp: short-term versus average
Background: I work for an Ambulance service. We are one of the largest ambulance services in the world. We have a dispatch system that will always send the closest ambulance to any emergency call. ...
3
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1answer
38 views
Inverse of itinerary function
Let $S^{-1}:\Sigma \to \Lambda$ be inverse of itinerary function. I showed that $S$ is continuous and bijective. How to show that $S^{-1}$ is continuous?
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1answer
85 views
Time-evolving probability distribution functions with an equation of motion
I came up with this question a while ago and haven't been able to gain any insight on it.
You are playing baseball. As a batter with finite vision capabilities, the only information you have about ...
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1answer
76 views
a mathematical model for file system
We are supposed to come up with a mathematical model describing a file system and its operations. The file system stores metadata in a database, and retrieves it when necessary. How does one go about ...
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1answer
101 views
Finding a logical expression (under some constrains) s.t. it is equivalent to another one
In this question, it was made clear, when
$\bullet$ some statement $A$ is stronger than another statement $B$, namely if $A\Rightarrow B$ holds; and when the statement $A$ is weaker than another ...
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1answer
47 views
Which variable represents the predator and which the prey.
Just a quick question I have the following system:
$$\frac{dx}{dt}=x\left(2-x-\frac{y}{1+x}\right),\qquad \frac{dy}{dt}=3y\left(\frac{x}{1+x}-4y\right)$$
It asks which variable represents the predator ...
0
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1answer
27 views
unit conversion doubt
Im a developer that likes maths, but dont have much experience,
I had constructed a graphic that animates a bar that grows on the X axis according to a value.
So, I have the values for the x ...
1
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1answer
1k views
How can I find the time constant of a first order system transfer function?
How can I obtain the time constant of the transfer function of a first order system, such as the example below?
$$ \frac{C(s)}{R(s)} = \frac{2}{s + 3}$$
Where $C(s)$ is the output of the system and ...
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0answers
29 views
using a scientific paper to model the temperature of pools in an irrigation system
Quite a general question...
I am referring to a scientific paper :
http://www.springerlink.com/content/41p817v1584q1850/
I am trying to model water temperature over a year.
I have the initial ...
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0answers
18 views
Another way to model depedency of phenomena given its observation history
Suppose we model two phenomena with its state functions, which is, rougly, a real function $f(t)$ on the time variable $t$. Now define the "similarity" of the two phenomena as the bounded linear ...
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190 views
In general, is it easier to solve problems that have random variables, or problems that are basically the same that don't [closed]
This question is asked because I don't understand how random variables will affect various math problems, and knowledgeable mathematicians would.
By easier, we mean less steps
If we make our own ...
2
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2answers
207 views
Recommended book on modeling/differential equations
I am soon attending a undergrad course named differential equations and modeling. I have dealt with differential equations before, but in that course just learned a bunch of methods for solving them. ...
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1answer
16 views
Smoother Generalized Mixed Linear Models
I wondered if anyone could help me figure out what a smoother was in regard to Generalized Mixed Linear Models or point me in direction of some relevant litterature.
Regards!
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1answer
183 views
Binary Logistic Regression Model Processing
Thanks for showing interest and wanting to help out.
My aim is to develop a model that - as accurately as possible - predicts how entities in a population will either cooperate or defect, as a % of ...
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0answers
46 views
Measuring Model Bias
If given the choice between two statistical models (for argument's sake, let's say Model 1 is $y = \beta_0 + \beta_1 x_1 + \epsilon$ and Model 2 is $y = \beta_0 + \beta_1 x^2_1 + \epsilon$), is there ...
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0answers
66 views
Finding Quickest Route for delivery using MATLAB with mathematic modelling
I have the question:
You have just set up a new business delivering water by truck to various farms in your
community (shown below). The diagram shows distance in km between the farms
with the ...
0
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1answer
25 views
Is there a statistic model that selects attributes in each state?
Every state has its own sub-attributes,
for example,
state S{ATTR1, ATTR2, ATTR3}.
We can train the model use data with states filled with all three attributes.
When we want to predict, we just want ...
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2answers
244 views
Sound Triangulation
Hello guys I would appreciate it if someone could help me out here. I have been asked to create a simple visualization for an assignment. I am required to triangulate the source of a artillery cannon ...
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3answers
271 views
Predicting the next vector given a known sequence
I have a sequence of unit vectors $\vec{v}_0,\vec{v}_1,\ldots,\vec{v}_k,\ldots$ with the following property: $\lim_{i\rightarrow\infty}\vec{v}_{i} = \vec{\alpha}$, i.e. the sequence converges to a ...
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0answers
83 views
Modelling randomized cup stacking, animal behaviour
This question has no scientific relevance for me whatsoever, but is a real life question which left me puzzled for a while. Even though I am not going anywere with this, maybe there is still somebody ...
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0answers
95 views
Non Dimensionalization
Could anyone of you suggest how to non-dimensionalize the following?
I have $e^{-6(x_{2}-x_{1})}$ where $x_{2}$ and $x_{1}$ are dimensional. I then let
$x_{2}=L \tilde{x}_{2}$, ...
2
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1answer
53 views
64 possible values - continuous or discrete?
I have a response variable in a model that is calculated from binary values of an 8x8 grid of pixels, giving a proportion. Technically, there are only 64 possible values the result can take, so would ...
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131 views
Phase Plane Analysis
Classify the fixed point at the origin and sketch an accurate phase portrait for the following system:
$$dx/dt = 36x-16y$$
$$dy/dx = -3x+28y$$
Am I correct in thinking that I need to write these two ...
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17 views
Variance estimate of small “meta-set”?
I've got two sets $A$ and $B$, both with $n=2$ elements / measurements. The variance of both can be assumed to be similar / depend on the same measurement error-function. I need to compare (with a ...
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1answer
227 views
How to derive and solve a difference equation.
I am having terrible trouble with the following question:
Suppose that $x_n$ is the amount owed on a mortgage after n years, £$m$ is the monthly repayment and $r$ is the annual percentage interest ...
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2answers
73 views
Multiple regression with model $Y = (1 + c_1X_1)(1 + c_2X_2)\ldots(1 + c_nX_n)$
I'm currently working with data contained in $Y, X_1, X_2, \ldots, X_n$ and wish to fit it to the model:
$Y = (1 + c_1X_1)(1 + c_2X_2)\ldots(1 + c_nX_n)$
where the $c_i$ are coefficients to be ...
1
vote
1answer
55 views
Reduce a range of values
I am using this weighted sum from the question How to build a function that gives recent years higher weight?
To reduce the value I tried square root of $X,$ then tried the $8$th root, ...
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2answers
126 views
How to determine units in a partial differential equation
How do we determine the units used in a differential equation? Yes, in theory a PDE has nothing to do with units, but I'm interested in this question from a modeling point of view. By units, I mean ...
2
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0answers
188 views
Finding a model for multiple non-linear regression
I want to implement a regression analysis, but I have problems with finding a model for the given data. There are $149$ $(x,y,z)$-values. $y$ values are all positive, $x$ is between $[-10, 10]$ and ...
0
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0answers
82 views
Figuring out MEMS gyroscope measurement's standard deviation from data sheet
Is it possible to figure out standard deviation of Invensense ISZ500 / IDG500 MEMS gyroscope angular velocities measurement $\mu$ from datasheet? I'm guessing, if at all, the necessary data are ...
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57 views
Modeling with a Bivariate Gaussian Distribution
In an earlier question I inquired about contour lines reflecting probability values in a Bivariate Gaussian Distribution. I have spent some time thinking and playing around with a Mathematica ...
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229 views
How do I turn this piecewise function into a “normal” function?
I am a Java developer building a web app that I will be deploying "in the cloud" (I hate that expression) in a few months. I'm trying to develop a function that will let me spawn and kill the right ...
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0answers
95 views
Check my solution - Modelling of a spring with Differential Equation
I am doing some work with differential equations. I have solved the following problem but am uncertain if I'm doing it correctly. Could someone look over it for me and check if I'm doing something ...
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2answers
125 views
What is the underlying function?
I have some value pairs. They are inversely proportional. I want to have a formula to get the second value from the first value.
...
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3answers
192 views
Mathematical (or physical) formulation of life
I recently started to have interest in the characteristics of life. Especially, I wonder if there are some kind of mathematical description of the true meaning of life and how it is emerged. Why does ...
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1answer
109 views
Mathematical idea behind tax bracket
This may be a lame question. The tax bracket is a way to calculate the tax based on the taxable income. For example
Imagine that there are three tax brackets: 10%, 20%, and 30%. The 10%
rate ...
