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James Tursa


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3,230 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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Answered
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...

2 hours ago | 0

Answered
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 ...

9 hours ago | 1

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

9 hours ago | 1

| accepted

Answered
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...

9 hours ago | 0

Answered
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....

1 day ago | 0

Answered
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...

1 day ago | 1

Answered
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...

3 days ago | 1

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Answered
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 ...

5 days ago | 0

Answered
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);...

5 days ago | 0

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

5 days ago | 0

| accepted

Answered
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'||...

5 days ago | 0

| accepted

Answered
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...

7 days ago | 1

Answered
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...

7 days ago | 0

Answered
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...

12 days ago | 0

Answered
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...

14 days ago | 1

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Answered
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...

15 days ago | 0

| accepted

Answered
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);...

16 days ago | 0

Answered
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: ...

16 days ago | 1

| accepted

Answered
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...

1 month ago | 1

| accepted

Answered
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 ...

1 month ago | 1

| accepted

Answered
Plotting a System of Two Second-Order Differential Equations
You've got a 4th order system, so your initial state must contain four elements including the x1' and x2', not two. E.g., [t, ...

1 month ago | 0

| accepted

Answered
hex2num can't recover value from the hex by num2hex
Try typecast(uint32(hex2dec('be361af6')),'single')

1 month ago | 1

Answered
Rotation order of quatrotate
I suppose this drawn out explanation is long overdue in this forum, so forgive me for being verbose, but a lot of posters have h...

1 month ago | 0

Answered
Comparing any of the matrix input
Hints: What does this result give you: classes == x Then look at this: doc any

1 month ago | 0

Answered
()-indexing must appear last in an index expression.
You've got closing and opening parentheses next to each other: ...)(... MATLAB thinks you are trying to use the second part as...

1 month ago | 0

Answered
Single precision matrix multiplication
To illustrate what Matt is saying, a simple timing test: >> format longg >> S = round(10000*single(rand(5000)+rand(5000)*1i));...

1 month ago | 2

Answered
Using MEX file with the main program of Fortran code
You would need to turn the PROGRAM line into a MEXFUNCTION line and add some code for getting the MATLAB variable data to/from t...

1 month ago | 0

Answered
An explicit Runge Kutta of Fourteen Order code
4th Order RK is here: https://en.wikipedia.org/wiki/Runge%E2%80%93Kutta_methods

1 month ago | 0

| accepted

Answered
Why does mxSetDoubles crash this MEX file?
This line is crashing your code: mxSetDoubles(plhs[0],a); You can't re-use data pointers this way. You have essentially share...

1 month ago | 0

Answered
Highest power of 2 that divides n.
In addition to David's comments, you need to do all of the calculations symbolically, so all of these should be sym: 2, i, r.

1 month ago | 0

| accepted

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