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Last seen: ungefär en månad ago Active since 2018

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Question

Difference between numerical and analytical solution of ode?
I am solving two differential equations numericaly and analyticaly. But when I compare results, they are not the same, I cannot ...

4 månader ago | 1 answer | 0

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Question

Matlab does not plot data which are mirrored data
I have variable r with dimension [1x2002] and values r = [1 0.9 0.8 0.7 . . . 0.7 0.8 0.9 1] and variable u0 with dim...

mer än ett år ago | 2 answers | 0

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Question

bvp4c: Too many input arguments error
I need to solve two differential equations of the first order, with one unknown parameter in each equation, and I have four boun...

mer än 2 år ago | 1 answer | 0

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How to solve first order ode with two boudary conditions?
I need to solve numericaly differential equation of the first order, where I have given values at the beginng and at the end of ...

mer än 2 år ago | 0 answers | 0

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Question

Solve system of two differential equations with bpv4c
I need to solve system of two equations with bvp4c method, where p is the pressure and it is only function of longitudinal coord...

mer än 2 år ago | 1 answer | 0

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Question

How to solve first order differential condition with two initial conditions?
I had system of equations defined in m file fun_zap_ri.m: function [f, R] = fun_zap_ri(z, p, beta, ri) R = ri - z .* (ri - 1);...

mer än 2 år ago | 0 answers | 0

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Question

Plot legend - cyrilic?
I need to make cyrilic legend in Matlab plot. I am doing it with: legend({'прва.'}, 'Fontname','Times new roman', 'FontSize', ...

mer än 2 år ago | 0 answers | 0

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Question

How to show first value on axis cuted with xlim?
I am using xlim to make my axis shorter, but on that way Matlab does not show me first value on shorter axis. More detailed: I...

mer än 2 år ago | 3 answers | 0

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Question

Plot and zoom in - axis labels doesnt work?
I am using nxt code to make my plot: figure; set(0,'defaulttextinterpreter','latex'); set(0, 'defaultAxesTickLabelInterpreter...

mer än 2 år ago | 0 answers | 0

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Question

How to load data from Simulnik Thermal House example?
I am trying to make Simulink example Thermal house (https://www.mathworks.com/help/simulink/slref/thermal-model-of-a-house.html)...

mer än 2 år ago | 1 answer | 0

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Question

Function call in ode45 does not work?
I have function: function [f,R]=fun_zap_ri_07(z,p) beta=1; ri=0.7; R=ri-z.*(ri-1); f=zeros(4,size(p,2)); f(1,:)=-3...

nästan 3 år ago | 1 answer | 0

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Question

How to get nearest values in matrix and save indexes of these values?
I have values saved as pi=[5 10 15]. And I have another values saved in puk, which is 401x1 double. I need to find values in...

mer än 3 år ago | 1 answer | 0

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Question

Change dashed line spacing on plot
I need to plot 6 different black lines on plot, and all of them need to be lines (without markers). The problem is there are onl...

mer än 3 år ago | 1 answer | 0

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Question

How to extract value from cell, then from matrix?
I have data stored in p, as 1x41 cell. For me it is necessary to extract every value in cell, every 101x4 double as matrix and t...

mer än 3 år ago | 1 answer | 0

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Question

How to fill matrix in for loop?
I need to fill matrix r, where r=r(z), and ri is constant. But with this code I onlu get the first row where r=-0.7:0.7. z=-1:...

mer än 3 år ago | 2 answers | 0

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Question

How to construct matrix for variable radius?
I have divergent geometry, where my longitudinal coordinate is: z=1:-0.001:0; Wall of the pipe is defined with this law: ri=0...

mer än 3 år ago | 1 answer | 0

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Question

How to change ode45 from solution for range of values, to solution just for one value?
I have next function file: function [f,R]=fun_z3(z,p) beta=1; ri=0.7; R=ri-z*(ri-1); f=zeros(4,size(p,2)); f(1,:)=-32.*bet...

mer än 3 år ago | 1 answer | 0

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Question

ode45 and sol structure - different results
I am using ode45 function to get solution of system of equation with this line of code [zv, pv] = ode45(@fun2, [1 0], [1; 0...

nästan 4 år ago | 1 answer | 0

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Question

How to extract variable from function file, and how to check is that result real?
I am using matlab function file to solve system of differential equations, and I have variable R in my function file. ...

nästan 4 år ago | 1 answer | 0

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Question

ode 45 - different results with different coordinate set
I am solving system of next equations: function f=fun(z,p) R=1; sig=1; beta=1; f=zeros(4,1); f(1)=-32*1*be...

nästan 4 år ago | 0 answers | 0

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Question

Increase precision of vpasolve method?
I am using vpasolve method to find solution of equation. It is necessary to compare solution with vpasolve for y with numerical ...

nästan 4 år ago | 0 answers | 1

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Question

How to find second derivative as output of ode45?
I am using ode45 function to find numerical solution for my system of equations, where I have 4 equations and 4 variables, with ...

nästan 4 år ago | 1 answer | 0

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Question

Is it possible to solve this equation symbolicaly with Mupad?
I am trying to solve equation symoblicaly with Mupad, where on the left side I have differential of p3, and on the right side I ...

ungefär 4 år ago | 1 answer | 0

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Question

vpasolve and for loop
I am trying to solve numerically symbolic equation. But one variable in my equation is series of values zv=1:-0.1:0 So,...

ungefär 4 år ago | 0 answers | 0

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Question

Solve equation numerically Matlab-Mupad
I am using Matlab, and I am considering to use Mupad to solve next differential equation: x^2+16*Kn_e*x-1-16*Kn_e-16*Kn...

ungefär 4 år ago | 0 answers | 0

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Question

Accuracy of the first derivative with ode45
I am using ode45 to get solution of system with 4 differential equation of the first order. ode45 gives me result as value, but ...

ungefär 4 år ago | 1 answer | 0

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Question

second order ode45-where to put boundary and initial condition?
I am solving this equation with ode45 method, p0 is already known: 4B*d^2u/dr^2+(4B/r)*du/dr=dp0/dz and I have two conditi...

mer än 4 år ago | 1 answer | 0

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Question

How to add variable to ode45 method?
I am solving system of two ODEs with ode45 method, and code is working for constant cross section, that means constant radius R:...

mer än 4 år ago | 1 answer | 0

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Question

How to use numerical solution in differential equation?
I have numerical solution for variable p, which I got through ode45 method. I need to calculate u, where u=((r^2-1)/16)*dp/d...

mer än 4 år ago | 1 answer | 0