# Torsten

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**Content Feed**

How to solve coupled second order ODE?

b = 0.1; fun = @(t,y)[y(2);-b*y(2)*sqrt(y(2)^2+y(4)^2);y(4);-b*y(4)*sqrt(y(2)^2+y(4)^2)]; y0 = [0;44.5;80;0]; tspan = [0,10];...

8 hours ago | 0

Getting the summation of a series

h=[ 1 3 5 7 9 11 13 15] ; ah = [35.8577 -6.2962 -1.2855 3.9251 -3.8197 2.2690 -0.4077 -0.9397 ]; alpha = lins...

9 hours ago | 1

| accepted

Using fminsearch() for MSD system

p0 = [50 400]; p = fminsearch(@fun,p0) function objective = fun(p) k2 = p(1); c2 = p(2); %tspan = [0,0.3]; %observing sys...

14 hours ago | 0

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Create a unit vector from two locations?

is this correct? No. MTH2 = [0.472 1.364 0.06] CoM = [0.471 1.147 0.903] UnitVector = (CoM - MTH2) / norm(CoM - MTH2)

14 hours ago | 0

how to use derivative of function using gradient?

Forget about y(13) and use dydz(2) = y(3); %Specific mass balance (CH4) dydz(3) = ((y(1)*y(3))+(dens_cat_weighted*r_CH4))/(D_m...

14 hours ago | 1

How to solve differential equation including derivative of eigenvalue of tensor?

See if it works. I cannot test it. syms s A = sym('A',[3 3]); % Define characteristic polynomial determinant = det(A-s*eye(3...

15 hours ago | 0

Solving a numeric equation matlab shows results with up to 32 decimals. How can I get this for the operation below for Exmpl? format longE for Exmpl. allows only 16 digits.

digits(100) vpa(sqrt(sym('3')))

17 hours ago | 0

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Minimalization problem LinearConstraint and conjugate gradient optimizer

According to the Python code, F is maximized, not minimized. Change in the below code if appropriate. M = [0.170543 0.327434 0....

17 hours ago | 0

Performing Chi Square Test

Source: https://de.mathworks.com/matlabcentral/answers/96572-how-can-i-perform-a-chi-square-test-to-determine-how-statistically...

1 day ago | 0

Substitute symbolic matrices into numerical matrices

Do you know Cramer's rule ? A = sym('A',[3 3]); b = sym('b',[3 1]); x = sym('x',[3 1]); sol = solve(A*x==b,x) And now pleas...

1 day ago | 0

System of Nonlinear Equations are failing to be solved

In my opinion, it should be eq1 = C_arg + P_arg == pi-phi_m*pi/180; instead of eq1 = C_arg + P_arg == pi-phi_m*180/pi; (see ...

1 day ago | 1

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Force a starting point on exponential graph

You must normalize to time = 0, not time = 24.4. The initial mass is the key, not the mass when already 24.4 (whatever) have pa...

1 day ago | 0

How do I write the below code in efficient way in MATLAB?

Q = [16,32,64,128,256,512,1024]; VEC=[0.2380 0.2380 0.2380 0.2380 0.2380 0.2380 0.2380 1.1898 1....

1 day ago | 0

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Please help me in plotting the following functions.

Limits of Euler's beta function are 0 and 1, not a and b. So C_m,i^nu = beta(i*nu+3,(m-i)*nu)/beta(i*nu,(m-i)*nu) + 2 and th...

1 day ago | 0

How to plot 4 curves with different constants?

y = @(C,x) (C-x)./(1+x.^2); C = [1 2 3 4].'; x = -2:0.1:2; plot(x,y(C,x))

3 days ago | 0

Use of 'ArrayValued' in Matlab numerical integration

f = @(x) 5*ones(size(x)); integral(f,0,2)

4 days ago | 1

How to write a code that takes a vector and outputs true if its the same forwards as it is backwards and false if not?

https://de.mathworks.com/help/matlab/ref/flip.html answer = isequal(v,flip(v))

4 days ago | 1

Unable to perform assignment because the size of the left side is 360-by-1 and the size of the right side is 360-by-360.

Elementwise division is required: hip_percent(:,2) = 0.14*asis_d./hip_d + 0.5*(hip_d - asis_d)./hip_d; or simpler hip_percent...

4 days ago | 0

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angle function in matlab formula

It's all written in the MATLAB documentation of "angle": Algorithms angle takes a complex number z = x + iy and uses the atan2...

4 days ago | 1

Using anonymous functions with vectors of unknown number of elements and getting the coefficients associated with the variables

Then n_s = 2; u = randi([-9999, 9999], 1, n_s) c = sym('c',size(u)); kappa = expand((1+u*c.')^2) coefficients = coeffs(ka...

4 days ago | 1

| accepted

Nonlinear regression not working

clc; clear all; input0= [160 159 158 157 156 155 154 153 152 151 150 149 148 147 146 145 144 143 142 141 140 139 138 137 136...

4 days ago | 0

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Find close points in two matrices of coordinates

Use "pdist2" to calculate the distances of the sites of the first set to the sites of the second set. Check which rows of the d...

5 days ago | 0

How to fasten the loop

Maybe there are faster commands than arrayfun for extracting the elements of LONG in cell arrays that correspond to sequences of...

5 days ago | 0

Normal random number generation

pd = makedist('Normal'); t = truncate(pd,0,1); r = random(t,1e6,1); figure(1) histogram(r,100) Or directly: r = -sqrt(2)*e...

5 days ago | 1

cumsum function question for integration

cumsum(y_cos*inter_val); is a Riemann sum for the integral of sin(t) - integrated between 0 and x. But the integral of sin(t) ...

5 days ago | 1

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I want to do exponential fitting for power decaying with time

x=[ 65.10 1.0000e+000 65.90 61.0843e-003 70.30 21.3693e-003 ]; fun = @(p)exp(-p*(x(:,1)-65.1)); f...

5 days ago | 0

How to define an ellipse by the eigendecomposition of its transformation matrix?

phi = linspace(0,2*pi,100); S = [1 0;0 4]; xy = S*[cos(phi);sin(phi)]; theta = pi/4; Sxy = [cos(theta) -sin(theta);sin(theta...

5 days ago | 2

| accepted

I have some coupled nonlinear ordinary differential equations. Three equations have three 2nd order derivative coupled together. Can someone tell me how I can get the response

Solve the third equation for theta_dotdot and insert this expression in equations (1) and (2). Then use the usual substitution...

5 days ago | 1

| accepted

When calling a user defined function, MATLAB throws an error for simple matrix multiplication

"const1" and "const2" are not visible in "planck_function" since you didn't declare them as "global" in the calling program. Bu...

5 days ago | 0

How can i use optimproblem as a free derivatives method?

https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=8736798

6 days ago | 0