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# James Tursa

##### Last seen: Today
3 241 total contributions since 2007

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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Can't figure out what I am doing wrong. Looking to find square root using the equation given x=(x+x/a)/2. I also feel like I am not making use of the approximation errors ea and es.
You can't do these assignments in this order: x_old=x; ea=((x-x_old)/x)*100; The first one will cause the second one ...

ungefär 19 timmar ago | 1

Coupled second order ODE with three variables
Problems: 1) Units. You really should annotate ALL of your constants with descriptions and units so that the reader knows what...

en dag ago | 0

How to split 3d matrix into sub-2d matrices?
I agree with Bob ... just using indexing downstream in your code will be much easier. If you really do need them in separate va...

2 dagar ago | 0

ODE45 to solve vector ode
You have a six element state vector. The y(1) and y(2) coming into your derivative function are not position and velocity vecto...

5 dagar ago | 1

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code in script called swap
You can adapt the three lines of code found here: https://www.tutorialspoint.com/learn_c_by_examples/swapping_two_numbers_using...

5 dagar ago | 0

Extract values common to 5 columns
Hint: Look at the result of diff(A,[],2). If all the values in a row are equal, what would you expect to be in the result of th...

5 dagar ago | 0

Element-wise power resulting in imaginary values and NAN
Looks like the problem calculation is being done in the background as exp(B.*log(A)), but I don't know why it does this sometime...

5 dagar ago | 0

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How to make a loop that writes in a new vector only values that meet a condition?
Assuming you don't want the first value since there is no previous value to compare to: x = [false, diff(VPo) > 0]; VPoF = VPo...

5 dagar ago | 0

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Out of Memory error when removing columns of a big matrix .
What are you doing with the matrix A downstream in your code? Even if the column removal worked, seems like you still might hav...

5 dagar ago | 0

Choose random element of vector
k = sort(randperm(numel(vector),2)); x1 = vector(k(1)); x2 = vector(k(2)); This assumes that you always want to be able to pi...

6 dagar ago | 1

Angle betwen two 3d vectors in the range 0-360 degree
E.g., here is one method: function a = vecangle360(v1,v2,n) x = cross(v1,v2); c = sign(dot(x,n)) * norm(x); a = atan2d(c,dot...

6 dagar ago | 0

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Internal variables not calculated
Maybe the behavior you are looking for is nested functions. Instead of a function at the end of a script, you have a function w...

7 dagar ago | 1

Internal variables not calculated
You didn't declare those variables global in the caller. You only have them global in the function. Add the global statements ...

7 dagar ago | 1

creating an 8x8 matrix using "diag"
2*eye(8)

7 dagar ago | 1

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how can i resolve this equation Runge kutta method
You've got a 2nd order equation, so that means you need a 2-element state vector. The two states will be y and y'. All of your...

7 dagar ago | 0

Appending to an array/vector
We would need to see your code to give a more specific answer, but the general outline is to index into your result vector. E.g....

8 dagar ago | 0

what wrong in my code when i use ode 45,and what the error are mean
Try changing this [t,y]=ode45('Mass_On_Stick_012345678',tSpan,y0,opts,Parameter); to this [t,y]=ode45(@(t,y)Mass_On_Stick_012...

8 dagar ago | 1

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dgemv produces only zero vectors as results
Two things: 1) All of the integers that you are passing into BLAS/LAPACK functions should be the same. Why are you using ptrdi...

10 dagar ago | 1

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Create an .m file
To create an .m file for a function named randint, you can do this at the command line as long as the default directory is your ...

12 dagar ago | 0

How to read a binary file with below description?
E.g., fname = the name of your binary file fp = fopen(fname,'rb'); k = fread(fp,6,'int16'); y_start = k(1); y_end = k(2);...

12 dagar ago | 0

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Output argument is not assigned on some execution paths.
What happens if you change this elseif imbalance <= 0 to this else

12 dagar ago | 0

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Does this character vector match any of the following character vectors?
You could use cell arrays. E.g., use ismember(currentMonth,{'June','July','August'}) instead of strcmp(currentMonth,'June'||...

12 dagar ago | 0

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I am getting wrong answer for factorial(22)
R2016a PCWIN64: >> a1 = factorial(22) a1 = 1.124000727777608e+21 >> b = (sqrt(2*pi*22))*(22^22/exp(22)) b = 1.11...

14 dagar ago | 1

generating random values with condition
You could use this FEX submission by Roger Stafford for each 4 number block: https://www.mathworks.com/matlabcentral/fileexchan...

14 dagar ago | 0

How to Convert a function return is a Handle (C++ mex)
DEVICE_HANDLE is a pointer, so if you are running 64-bit MATLAB then DEVICE_HANDLE will be be 64-bits and will not fit in a 32-b...

19 dagar ago | 0

Runge kutta 4 with two ODE's - function inside a function
Since W is a function of time, it needs to match the time that you are using in each particular line of code. E.g., take this l...

21 dagar ago | 1

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Converting output from 'find' into a logical
E.g., x = the result of the find y = false(22879,1); y(x) = true; But it may be better to create y with a direct logical exp...

22 dagar ago | 0

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Remove all infinite values from ydata and then remove those same indices from the xdata so the vectors remain the same length
x = isinf(ydata); ydata(x) = []; xdata(x) = []; Or, if you need to extract the values into new variables, x = ~isinf(ydata);...

23 dagar ago | 0

Different results by changing the order of operations
You haven't broken up the calculations properly. I.e., you are comparing different calculations. Your code is essentially: ...

23 dagar ago | 1

| accepted