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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...

etwa 4 Stunden 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 ...

etwa 11 Stunden ago | 1

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

etwa 11 Stunden 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...

etwa 11 Stunden 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....

ein Tag 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...

ein Tag 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 Tage 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 Tage 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 Tage 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 Tage ago | 0

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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 Tage ago | 0

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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 Tage 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 Tage 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...

13 Tage 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...

15 Tage 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 Tage ago | 0

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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 Tage 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 Tage 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...

etwa ein Monat 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 ...

etwa ein Monat 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, ...

etwa ein Monat ago | 0

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

etwa ein Monat 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...

etwa ein Monat ago | 0

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

etwa ein Monat 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...

etwa ein Monat 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));...

etwa ein Monat 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...

etwa ein Monat 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

etwa ein Monat 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...

etwa ein Monat 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.

etwa ein Monat ago | 0

| accepted

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