# Mischa Kim

### MathWorks

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Professional Interests: Spacecraft dynamics and control, numerical analysis, simulation, animation

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**Content Feed**

Properties of exponentials - symbolic algebra

Hi Luca, use syms x y z = simplify(exp(x)*exp(y))

10 mois ago | 0

how to make matlab functions work not starting at the first element

Hi Naufal, how about: a = [2 5 2 4 2 7 2 2 2 5 2]; pks = findpeaks(a); mypks = pks(2:end); To be able to skip the firs...

environ un an ago | 0

Question about plotting graph.

Hi, how about plot(T0,y,'ro') Since this is only one single data point it is hard to see in the plot, hence I change the color...

environ un an ago | 0

Problem in displaying or printing final result.

Hi Masoud, use fprintf instead. Check out the examples in the link.

environ un an ago | 1

| accepted

why didn't the event function detect the events?

In your ode45 call you are not returning any event information. Replace with [tout,yout,te,ye,ie] = ode45(@Tq_Tj,tspan, y0,opti...

environ un an ago | 0

Basins of attraction and Newtons Method.

One problem was in the governing equations for f. I cleaned up a bit and this works now: % Governing equations f = [-7.716*1e-...

environ un an ago | 0

Empty windows in EditFields of app.designer?

ErikJon, as a workaround you could use an Edit Field (Text) instead of Edit Field (Numeric). The drawback of this workaround is ...

environ un an ago | 0

| accepted

Getting extra parameters from ODE45 and the mystery transpose

Hi Simon, to your first question: When you assign values to dx(1), dx(2), and so on you are creating a row vector. However, you ...

environ un an ago | 0

| accepted

How to solve the error "[t, z]= ode45(@observer, t_temp,z0)" in line 23.

dzdt seems to be a (3x2 ?) matrix. It needs to be a 3x1 vector to be consistent with the initial conditions, z0, which is also a...

environ un an ago | 1

| accepted

Why am i receiving "Error:Invalid expression. When calling a function or indexing a variable, use parentheses. Otherwise, check for mismatched delimiters."? for S(K)>0

Hi, since you do not know the number of iterations it makes more sense to use a while instead of a for loop: while S(K)>0 %as l...

environ un an ago | 1

| accepted

How to count the number of different strings in a string list?

Hi, use str = {'AAA','ABB','CDE','ABB','CCR','AAA','FDR'}; numstr = numel(unique(str))

environ un an ago | 0

| accepted

How to extract value at a given time in ode 45

Hi Shubham, use an events functions, see the example below. With events functions you can identify zero crossings; in your case ...

environ un an ago | 0

| accepted

Draw a circle on matlab app designer?

Hi ErikJon, if the plot input is a matrix (e.g. your circ) "...the plot function plots the columns of the matrix (circ) versus t...

environ un an ago | 0

| accepted

please help me (dsolve)

Use instead syms y(t) eqn = diff(y,t,2) + 0.5*diff(y,t) + y == 3; Dy = diff(y,t); cond = [y(0) == 0.5, Dy(0) == 0]; w ...

environ un an ago | 0

confusing ode suits for solving discontinuous odes

Hi, this is because the integrator, ode45, adjusts the integration step size. Broadly speaking where the dynamics is more comple...

environ un an ago | 0

| accepted

How to Find average value for every 10 sets of a matrix

Hi Magdy, you could use something like: x = 1:1:12; % this would be your matrix A y = reshape(x,3,4) m = mean(y,1)

environ un an ago | 0

| accepted

How to Use "Ask a Question" Section Correctly?

Hi Ercan, thanks for flagging this. I have seen the same behavior this morning in Chrome, other browsers seemed to work fine. I ...

environ un an ago | 3

| accepted

ODE Event Location detecting events other than zero

Hi Hariharan, yes it is. You simply define a function that is equal to zero whenever your expression equals a certain value. Fo...

environ un an ago | 0

| accepted

How do I change the values for x-axis ?

Hi Anne-Lise, do you mean changing the tick labels? See this answer. If this does not address your question, how exactly do you ...

environ un an ago | 1

Why is the resulting time-domain curve from Euler method and ode45 not stable?

Hi Ni Made Ayu Sinta Dewi, there is nothing you are doing wrong. What you are seeing is expected behavior. This is because you a...

environ un an ago | 0

| accepted

ode45 fail with pendulum

Hi Bobby, this is the wonderful world of numerical (vs symbolic) computation. ode45 is a numerical integrator that approximates ...

environ un an ago | 0

| accepted

Changing Length of Pendulum while it is in motion

Dear Yan Koon Ang, this is possible. In the example you are referring to in your question you would have to make the time varia...

environ un an ago | 1

I am trying to plot x and y with y being the only unknown but I don’t what is wrong in my code please help

Honore, the one thing I notice is that x and y are vectors. Rewrite the y-equation using the dot operator, .^ instead of just ...

environ un an ago | 0

| accepted

Finding the initial conditions which give a specified event using ode45

Patrick, as Walter pointed out this is a BVP. However, you can and I personally would use ode45 and the so-called shooting meth...

environ un an ago | 0

Differential equation by simulink

Double-klick on the integrator blocks and you'll see that the default initial condition is zero (0). It is also inside the integ...

environ un an ago | 0

when i run the code the plot graphs appears empty here is the code please help to find the mistake i made

Seif, I believe this is what you are trying to do: %calculating velocity V3 = 10; % velocity of the piston in cm/sec %global...

environ un an ago | 0

| accepted

How to change a Function by a Variable

Ercan, here you go, for the first term: syms phi x A B eq = A*sin(phi) + B*cos(phi) eq = subs(eq,sin(phi),2*x/(1+x^2))

environ un an ago | 1

| accepted

How to write Newton method with exact number of iterations and see all digit ? for example if method is required to take exact 5 iterations of newton's method

Add a loop index, e.g. ii. Also, you set your code as a function. This means you can call it, e.g., from the command window usin...

environ un an ago | 0

serie with two parameters

Sara, it really depends on what you are trying to achieve. For starters you could use two for loops to take care of the summatio...

environ un an ago | 0

Plotting a function with 2 dependent variables

Use meshgrid instead: [x,y] = meshgrid(-10:0.1:10); z = sin(x).*cos(y); plot3(x,y,z)

environ un an ago | 0