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# James Tursa

##### Last seen: Today
3,240 2007 年以降の合計貢献数

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

#### James Tursa's バッジ

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...

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...

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...

4日 前 | 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...

4日 前 | 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...

4日 前 | 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...

4日 前 | 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...

4日 前 | 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...

4日 前 | 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...

5日 前 | 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...

5日 前 | 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...

6日 前 | 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 ...

6日 前 | 1

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

6日 前 | 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...

6日 前 | 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....

7日 前 | 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...

7日 前 | 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...

9日 前 | 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 ...

11日 前 | 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);...

11日 前 | 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

11日 前 | 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'||...

11日 前 | 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...

13日 前 | 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...

13日 前 | 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...

18日 前 | 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...

20日 前 | 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...

21日 前 | 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);...

22日 前 | 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: ...

22日 前 | 1

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Grabbing sections of a matrix by using two doubles as the index
E.g., result = arrayfun(@(x1,x2)data(x1:x2),find(indStart),find(indEnd),'uni',false); This assumes of course that the indStart...

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1-2-1 or X-Y-X rotation matrix not supported
According to the doc here: https://www.mathworks.com/help/aerotbx/ug/angle2quat.html?s_tid=doc_ta The angle2quat supports the ...

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