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James Tursa


Last seen: 3 jours ago Active 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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Answered
Is it possible to process the sparse matrix faster with vectorization instead of for loop?
You need to re-evaluate how you are doing things. In the first place, you have the Euclidean calculation wrong. It should be thi...

7 jours ago | 0

Answered
How to exchange data between two C++ MEX files
Your current scheme is not foolproof. How does the 1st mex function know when it is safe to unlock and clear memory? How does th...

7 jours ago | 0

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Answered
How to solve Lc=y without backslash operator?
First, I am assuming there is a typo and the system you are solving is Ly = c, not Lc=y. Second, you made a good start by writi...

9 jours ago | 0

Answered
I am using euler's method to solve a differential equation, but when I run the code it doesn't plot.
Take a look at these lines: t0=0; %start time t1= 500; %finish time dt = 100000; Your stepsize is much larger than the total...

12 jours ago | 1

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Answered
Accessing struct using C library always NULL
Typically, it is best just to post your code so we can see exactly what you are doing, instead of posting a description of your ...

12 jours ago | 1

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Answered
Errors while trying to setup equation for root finding.
Did you mean multiply by the "a"? x_pdo = z_pdo/(1 + a*(k_pdo - 1)); x_water = z_water/(1 + a*(k_water - 1)); x_glycerol = z_...

12 jours ago | 0

Answered
How do I access a field from a function's input?
Assuming you are passing in a character string for freq, use this syntax: output = myStruct.(freq);

14 jours ago | 0

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Answered
How can I obtain the T and Y for R Runge Kutta method?
The first version has an error. This line: k3=h*feval(f,T(j),Y(j)); should be this instead: k3=h*feval(f,T(j)+h/2,Y(j)+k2/2);...

20 jours ago | 0

Answered
How to solve array indices error?
x1 = 0*ft; : distance1=sqrt((x1-x2)^2+(y1-y2)^2+(z1-z2)^2); : sp = distance1(x1,y1,z1,dx,dyv(i),dz); % incident di...

29 jours ago | 0

Answered
Solving ODE using Euler Method and 4th Order Runge Kutta Method
You pretty much have the Euler scheme worked out, so I will help you with a vector formulation. Take this code: for i=1:n ...

environ un mois ago | 0

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Answered
Problem finding sum of array using vectorization
The first element of x is 1, so that element produces 1/(1-1) = 1/0 = inf in the second line. You need to rewrite that second li...

environ un mois ago | 0

Answered
Multiplication of large matrix with its transpose
The fastest way is to simply write it as A * A', because MATLAB will see that the operands are the same and call a special multi...

environ un mois ago | 0

Answered
Solving ODE in MATLAB using Runge-Kutta method of order 4
Why aren't you using this to update z: z(i+1) = z(i) + (1/6)*(l1+(2*l2)+(2*l3)+l4);

environ un mois ago | 0

Answered
Why is the string type not implemented as standard type?
All of the standard full numeric types as well as char and logical are implemented as simple rectangular data arrays. The string...

environ un mois ago | 1

Answered
how to print randomly selected column?
Shouldn't that be size(data,2)? Also, generally you should be using string comparison functions for the tests, not the == opera...

environ 2 mois ago | 0

Answered
NaN shows up in matrix when solving my ODEs, how can I fix this?
"All of my matrices I am solving for have NaN after the third time line. How do I solved this issue?" Set up a breakpoint somew...

environ 2 mois ago | 1

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Answered
Mean of multidimensional array
Doesn't mean(mdar,3) do what you want?

environ 2 mois ago | 0

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Answered
Function Error: Array indices must be positive integers or logical values.
When you have parentheses appear on the left hand side of an assignment like this: v(ro,ri) = (sqrt(m/(ri)))*((1/sqrt(R))-((sqr...

environ 2 mois ago | 1

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Answered
MXCREATEDOUBLEMATRIX memory overflow error
Rather later for an Answer, but here goes anyway: You should never use literal integers for API calls, because you can't be sur...

environ 2 mois ago | 0

Answered
How can I solve x^4-1=0
doc roots

environ 2 mois ago | 0

Answered
Convert unsigned integer to decimal
Not sure what the real question is here. Does one of these do what you want? int1 = uint32(hex2dec('9d900000')); int1 = uint32...

environ 2 mois ago | 0

Answered
convert integer to bytes
Depending on what you are doing downstream with this, you can use the typecast( ) function. E.g., bytes = typecast(my_integer,'...

environ 2 mois ago | 0

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Answered
Selecting multiple different rows in a 3D matrix
You can use a vector for the indexing. E.g., x = matrix(:,:,[2:16,24:48]); Does that, or something like that, do what you wan...

environ 2 mois ago | 0

Answered
Using a variable vector in a loop
Suppose you store the column vectors in a matrix called V. Then vk would simply be V(:,k). And if the uj are stored in a matrix...

environ 2 mois ago | 1

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Answered
Fortran code in Matlab
I'm trying to figure out the purpose of the backslash \. If this was the last character in the format statement then I would ass...

environ 2 mois ago | 0

Answered
Assigning mxUint16 variable to plhs[0]
You cannot attach native C/C++ memory to an mxArray. The MATLAB API "mxSetEtc" functions check to see that the memory addresses ...

environ 2 mois ago | 0

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Answered
How to separate a vector into two different vectors?
Others have already pointed out better ways of doing this. But to answer your question as to why your current code is not workin...

environ 2 mois ago | 1

Answered
Nested "For Loop" Array Size
To keep the indexing the same, just use the top value from the loops. E.g., DataArray = nan(300,50,100,numel(inputValsY3)); No...

environ 2 mois ago | 0

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Answered
convert value from radian form to degree form
If you have values, then just number_in_radians = number_in_degrees * (pi/180); If you are working with trig functions, note t...

environ 2 mois ago | 0

Answered
Calculate taylor series using while loop
Looks like you are planning to use the identity ln(5) = ln((1/5)^-1) = -ln(1/5) and then use 1/5 as the x in the Taylor Series e...

2 mois ago | 0

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