# James Tursa

Interested in external applications, mex & engine applications with Fortran, C, C++, etc, particularly in the areas of speed improvement and memory management efficiencies.

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**Content Feed**

Solve 2nd order ODE using Euler Method

You start your loop with i=1, but that means your x_d(i-1) will be x_d(0), an invalid index, hence the error. You need to set in...

1 day ago | 0

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Finding a single root of x^(3.6)=75

Make a function handle with the @ operator. E.g., fun = @(x) x^(3.6)-75; x0=3; z = fzero(fun,x0) Check z^3.6 Or you can r...

1 day ago | 2

Need to find dot product between two second order tensor

If you change the inner loop calculation to this: w(i,k) = dot(S(i,:),u(:,k)); then you would have dot products between the S ...

2 days ago | 0

linear combination of vector and permutation

Another way very similar to Torsten's method, limited to two desired values: n = 3; 2*(dec2bin(0:2^n-1)-'0')-1

2 days ago | 0

Use trapezoidal method to find the deflection at each measurement point.

Sounds like you want the cumtrapz( ) function. If the assignment requires you to use loops, just code up the formula found in th...

5 days ago | 0

How to convert decimals to Ascii characters?

Your table isn't ASCII encoding of characters, so you can't use simple functions such as double( ) etc. You are probably going t...

6 days ago | 1

Trapezoidal numerical integration using for loops

See the Trapezoidal Method section here for the fomula: https://www.mathworks.com/help/matlab/ref/trapz.html?searchHighlight=tr...

6 days ago | 0

a)Extract the data from the two columns into separate arrays named time and distance. b) Determine the velocity and acceleration of the rocket. Use a FOR loop or as many as d

Hints for using a difference method: Velocity = Position / Time Acceleration = Velocity / Time To get the delta values, just...

6 days ago | 0

| accepted

Change of position of velocity vectors and time interval between the change

Looks like an orbit problem. Around the Earth, I presume? You will not be using the Symbolic Toolbox for this assignment. You w...

9 days ago | 1

Any comment to speed up the speed of caculation of symbolic loops having Legendre polynomials?

The Symbolic Toolbox is going to be slower than IEEE floating point ... that's just something you have to accept. And if you nee...

13 days ago | 1

Formula for norm(x)

This question appears to be a follow-up to this post: https://www.mathworks.com/matlabcentral/answers/1809695-what-exactly-norm...

14 days ago | 0

| accepted

what exactly norm(x) function do?

The equivalent function to norm( ) for a complex column vector x is sqrt(x' * x) where x' is the complex conjugate transpose. ...

14 days ago | 1

| accepted

Why am I receiving Not enough input arguments?

The error seems pretty clear, you are calling func( ) without enough input arguments. The func( ) signature has six inputs: fun...

15 days ago | 1

| 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

Another related approach is to isolate all the 2nd derivatives on the LHS and put everything else on the RHS. Then pick off the ...

15 days ago | 0

how to use exp for this problem

You need to use the * operator to multiply in the denominator. E.g., w=exp(-(i-Un)^2/(2*sd^2)) If i is not a variable defined ...

15 days ago | 0

Multiple Outputs of a function into a single vector

You could modify f( ) to return a vector. Or if you didn't want to modify f( ) you could create a helper function that does this...

16 days ago | 1

dynamic matrix with changing variable name in for loop

Do not dynamically name variables. This is bad programming practice and will leave you with hard-to-use variables downstream in ...

16 days ago | 0

ODE solver for restricted 3 body problem

In this line: dydt(2) = y(1) + 2 * dydt(3) - mu_p * ((y(1) + mu)/D1) - mu * ((y(1) - mu)/D2); you use dydt(3) before you set i...

17 days ago | 0

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Write a function file that computes the roots of a quadratic using the form for x+ and x−1 that are least susceptible to cancellation error.

Is this the type of formulae you are being asked to code? https://people.csail.mit.edu/bkph/articles/Quadratics.pdf https://st...

17 days ago | 0

How to get the same number of char as number of decimals using num2str?

You might look into using the fix( ) function to isolate the fractional part of your number and then work with that directly.

20 days ago | 0

matrix to struct do not match

You should really show us all of the actual code in question, not just a wordy description of the code. A better description and...

21 days ago | 0

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Assign elements in multidimensional struct to 2D array

You can use the vercat( ) function to force the comma-separated-list generated by C.pts to stack vertically: for ii=1:5, C(ii)....

22 days ago | 1

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Singular Value Decomposition calculation of a matrix

By changing the order of the rows you have changed the order of operations inside svd( ). The two answers are essentially the sa...

23 days ago | 1

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Issue with N body problem using ode45

You need to rethink your problem statement and initial conditions. The initial positions can't possibly be in the neighborhood o...

29 days ago | 0

What is the best function of the following shape?

There are lots of functions that could fit this general shape. E.g., sin(x), or more generally A*sin(B*x+C) depending on width a...

30 days ago | 0

Rotate an image 180 degrees without library functions

Hint: Take a small example, rotate it 180 degrees, and see where the elements end up. Then consider how you might get that resul...

1 month ago | 0

How to calculate the mean value of the non vero value in a vector?

Another way that doesn't require any data copying: M = [0.7,0.3,0]; sum(M)/nnz(M) Be aware that if there are no non-zero elem...

1 month ago | 1

Adding value from structure into a vector after each iteration of a for loop.

The reason you are getting a 2x8x2 answer is because you start with a 1x8 vector but then assign spots outside of those limits i...

1 month ago | 0

parallel sum different from serial sum

Bruno and IA have already given the reasons for this discrepancy. I would simply add that even though you are adding integers an...

1 month ago | 2