Questions regarding the plotting or graphing of functions. Questions about graphs with vertices and edges should use the (graph-theory) tag instead. (STUB)

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220 views

Recognizing subadditivity

Let $f: (0,\infty) \to \mathbb{R}$ be some continuous function. We say that $f$ is subadditive if the bound \begin{align} f(x+y) \leq f(x) + f(y) \tag{1} \end{align} holds. I was attempting to ...
3
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162 views

Sketching the graph of a function

How would I sketch the graph of the following function. Sketch the graph of a function satisfying the following conditions $f(1)=2$ $f(-1)=f(3)=-1$ $f'(1)=0$ $f'(x)>0$ for all $x<1$ ...
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29 views

Properties and representations of the the rescaled complementary error function $\mathrm{erfcx}{z}$

Consider the rescaled complementary error function: $$ \mathrm{erfcx}(z) = {e^{z^2}} \left( {1-\mathrm{erf}(z)} \right) $$ $z \in \Bbb{C}$ which also has the following integral representation: $$ ...
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48 views

$x^{y}=y^{x}$ Intersection Question

I'm looking at this problem, $x^{y}=y^{x}$ and the question is to find the point of intersection of the two curves that form a solution set. I understand how to find the point of intersection using a ...
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58 views

Should a “good” equation divide the plane?

At the question Is there any equation for triangle? (MSE) the answer given by Henning Makholm received the most upvotes. Therefore let's define the following triangle function $H$ with (a,b,c) the ...
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50 views

Using Graphs Changes the Solutions for Diophantine Equation? Imperfection of Graph?

Solve the Diophantine equation $$x^2+4y^2=z^2$$ The problem here is that I derived solutions using two different methods, and the both solutions do satisfy the given equation yet they are ...
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69 views

how to choose point spacing to approximate a parametric curve using line segments?

Suppose I have a parametric equation for a curve $\vec{r} = f(t)$, which I wish to draw using line segments between some set of points at times $t_0, t_1, t_2,$ etc. If I want to achieve a given ...
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148 views

Find a function (curve fitting) for given values

I am trying to assign scores for URLs based on their view counts. I have about 300,000 URLs. In a two-day interval, only 1 URL got more than 5000 views 8 got between 1,000 and 5,000 views about 500 ...
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102 views

Ellipse radius interpolation with different radiuses

I am writing a library for graphical LCDs and I want to incorporate a function to draw a circle on the screen. I have already succeeded in drawing simple circles, however, I want to be able to pass a ...
2
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75 views

planarity of graph as a consequence of its flow

Is it possible to distinguish planar and non-planar graphs (networks as a matter of fact) by flows? That is, is there a flow criterion for a graph being planar or not?
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133 views

My solution is right and the book is wrong (parabolas) or did I misunderstand it?

Find the equation of the parabola with the vertex at the origin; directrix 2x = 3 So what I did is, find the equation of the directrix $$x = \frac{3}{2}$$ and then because its the directrix, the ...
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177 views

how to obtain state space diagram and state space model for transfer function

How do we obtain the state space diagram and state space model for transfer function for example the question is given How to draw state variable diagram for the given transfer function ...
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23 views

Quartic Polynomial Manipulation

I have a quartic polynomial in $x$ (too long to write here) $f(x,c_1, c_2, c_2)$ where $c_1, c_2, c_3$ are constants which I have complete freedom over how to fix their values, as long as they are ...
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30 views

Plot histogram and density function

I need to plot a histogram for the data: ...
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38 views

What is the number of x-intercepts in this graph of sine?

The function : $y=3-4\sin(2\pi x-3\pi)$ .. how many $x$-intercepts over the interval $[0,2]$? I am confused if they're 3 or 5 because there are 3 $x$-intercepts that are really intercepting ...
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13 views

Shape of graph and plot

Suppose $x \in [0, \infty)$ and $y \in [-1,1]$. When we plot $y$ vs. $x$, we get an upward parabola shape. Suppose we plot $y^2$ vs. $x$. Would the shape also be approximately an upward parabola?
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29 views

How to find change points in a graph on matlab

I have a graph like this I need to find points at which sudden changes happening for the DPC Time Curve. We can observe that at time 20 and around 70 increase is happening. How to do this in Matlab. ...
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35 views

How to approach sketching sine and cosine graphs with transformations

Any tips or suggestions in sketching these graphs quickly, and in ONE go? In exams, I don't want to spend ages re-drawing the original sine/cosine graph, one by one, following each new ...
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79 views

Physical shapes you can't simulate using mathematical functions

This question borders philosophy, so I would be happy to move it somewhere else if this forum is inappropriate. While doing some 3D function plotting, it occurred to me that I can plot any shape ...
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15 views

Weighting values using curves

I am in the field of computer programming but I think my question is maths based. I have tried several google searches on this matter but nothing has come up with what I am looking for, probably ...
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32 views

How does sin & cos affect audio waves

Given a function such as "cos (x) + 4 sin (3x) + 5 cos (3x)" when graphing it to produce a wave, are there any set rules to how you can adjust the function to produce a higher frequency, or increased ...
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21 views

Online tools for plotting and deriving formulas from set of data?

I have a matrix of 20x3 decimal values. I would like to have them in a graph, with one plot for each of the three y values. I would also like approximated formulas for each of the three. Are there any ...
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32 views

Visualizing a complex curve

This may be as much a question about computers as about math. Let $C=\{f(r,s,t)=0\}$ be a curve in $\mathbb{CP}^2.$ By forgetting about the points at infinity we can view $C$ as a surface in ...
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66 views

How does a piecewise step function work?

The wiki pages aren't helping at all. What is a step function and how does it work? I've seen them used in the floor, ceil, frac and even signum functions. And although it is easy to understand what ...
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14 views

How an I create a model population?

I need to crate a model population for my Math fair and this is what I have. I need some help with it -I want to find out the size of a population by using a natural exponential function -When I ...
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56 views

“Strange” plot of a difference equation

In this book about intertemporal optimization (page 33) I've found this difference equation: $x_{t+1}=ax_t \quad, \quad a>0$ The solution is: $x_t=a^t x_0$ where $x_0$ is the initial value of ...
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49 views

Given only the graphical representation of a curve, how can I find the function?

I'm developing an application which will: A. identify curves in 2D images using the generalized Hough Transform B. determine from the graphical curve the mathematical function needed to generate it ...
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153 views

How to plot a stream function

This question relates to fluid mechanics and I have the components in polar coordinates. The components of the velocity field are; $$v_r= \frac{-kr}{z}$$ $$v_z= kz$$ $$v_\theta= 0$$ and I have ...
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93 views

Splitting parametric curve equation into two ranges

I am examining the speed of motion on curves and in the textbook i am reading , the example was showing that using a parametric equation for an ellipse will result in a regular motion (as expected) , ...
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58 views

Graphing cumulative elevation gain along a route

I'm trying to develop a formula that will allow for a graph of the cumulative slope elevation gain along a route to be created. Currently I am using the Max value of the elevation along the route ...
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601 views

Graphically solving a Linear Programming Problem?

I was given the following linear programming problem and have been asked to find all optimal solutions graphically. I am quite new to the subject, so please forgive my naivety. ...
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191 views

Help to understand the concept of diminishing returns

Suppose I have this function: $q=f(k,l)=600k^2l^2-k^3l^3$ Then, $f_l=1200k^2l-3k^3l^2$ $f_k=1200kl^2-3k^2l^3$ $f_{ll}=1200k^2-6k^3l$ $f_{kk}=1200l^2-6kl^3$ $f_{kl}=f_{lk}=2400kl-9k^2l^2$ Now, ...
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57 views

How to calculate straight line into graph having variety of different results

How to calculate straight line into graph having variety of different results. What I mean for example let say we have this kind of results (measuring persons weight ...
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206 views

Building mathematical graph of AC-DC voltage converter

    I build the math function that describes the graphical operation of an electronic Wheatstone bridge (full-wave rectifier). I arrived at the following solution I created a ...
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306 views

Easiest way to determine graph formula to predict disk space growth

Suppose I have several points on a two dimensional plot. Is there an online program (or open source or free tool) that can get the most accurate formula for my plotted points? Or if I were to do ...
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154 views

Graph for lower and upperside bound absolute value function

The relation to be represented in graph is as follows $$ y = k \text{ for } k-1 < |x| < k \text{ where } k\in \mathbb Z $$ Normally we plot the area where the relation holds good is where ...
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97 views

plotting the lagrangian

From the differential equation $$\frac{\partial P}{\partial r} = \left[1+\frac{r}{\ln(1+r)}\right]D$$ I get the second-order equation $$\frac{1}{D}{P(r)}=\text{Ei}\left(2\ln(r+1)) - ...
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73 views

3d Implicit Trigonometry help?

I'm trying to understand implicit 3D trigonometry, specifically with this equation: $$\sin(y)+\cos(z)=\cos(x)$$ Can someone please explain to me what is going on with this equation? I really can't ...
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103 views

Plotting characteristic equations maple

I'm trying to plot the characteristics for the following PDE with initial conditions: $$u_t +uu_x =0$$ where $$u(x,0)=a \ for\ x<-1, \ b\ for\ -1<x<1, \ c \ for\ x>1.$$ I'm first ...
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56 views

Regression with multiple line types from set of points

Given a set of points, I'm looking to find the best possible line (within reason) to fit to these points. These points won't be from real data, so they could form any sort of curve or line. So, I ...
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41 views

Dynkin diagrams

Let $\gamma$ be a tripple edged graph that is associated with an admissible set in a real inner product space. Please, how do I show that $\gamma$ is the Coxeter graph of the Dynkin diagram, $G_2$?
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45 views

Plotting the Kepler stars

Kepler Field of View I'm looking for a way to take stellar coordinates (right ascension / decliniation) and plot them, so that they look like the picture below. Kepler Projection (The goal) Normal ...
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47 views

How to plot functions of this form? $x^7-\sqrt y=$ constant +$\log(x)+e^y$ (of an equation between $x$ and $y$)

I need to know how to plot any kind of equation between $x$ and $y$ without solving it for $y$. For example, for $x^2+y^2=1$ I need the plot without knowing that $y=\pm \sqrt {1-x^2}$.
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280 views

Is there a name for this type of plot? (function on complex plane vs time shown in 3D)

I'm just looking for a name for this type of plot, which is time vs real part vs imaginary part shown as a space curve. Complex exponential: Used to explain chirplets: Complex Morlet wavelet ...
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43 views

A resource to browse various function graphs?

I couldn't find what I need from google, so I figured it's time to ask here. Basically I'm looking for something like an online catalogue for all kinds of function graphs. I need a few specific ones ...
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126 views

Variation on shortest path

I have the following problem. Given a directed graph $G=(V,E)$ with edge costs $c_{ij}$ between all edges $\{i,j\}$. We have multiple sources, say $s_1,\dots,s_k$, and one target, say $t$. The problem ...
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65 views

Proving That The Graph Is Symmetric About The Origin

I know that the graph of an equation in x and y is symmetric with respect to the origin if replacing x by -x and y by -y yeilds the same equation. How can one prove that if the graph is symmetric ...
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41 views

Graphing a curve for cumulative repayments

I have a formula in an excel spreadsheet that calculates compounding interest over a period of time in 20 different cells, reducing the amount in each increment using the following formula: ...
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620 views

Radial profile from a Cartesian plot

I'd like to calculate a radial profile of a 2D Gaussian. it should be a half of a Gaussian, maximum of about 3000 at $R=0$. If I plot radial positions $\left(\sqrt{x^2+y^2} \right)$ of every ...
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30 views

Exercise about vector functions of real variable

Parametrize in a clockwise direction by means of a continuous vector function into pieces, starting at the point $(1,1)$ the following curve. (Sorry for my bad English) $$c:\begin{cases} { \left( ...