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James Tursa


2,858 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
summation of sinx using summation
You are missing the alternating signs of the terms. E.g., you could put in a factor of (-1)^something to get this effect. The ...

1 day ago | 0

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How to concatenate each row of a matrix into a vector ?
result = char(A+'0');

1 day ago | 1

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Index exceeds the number of array elements (1)
Type the following at the command line: dbstop if error Then run your code. When the error occurs, the code will pause at that...

4 days ago | 0

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How to correct "Parse" error
Don't have your function at the top of this. Put it at the end or in a separate file. E.g., t = 1; while (height ~=0) h =...

8 days ago | 0

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I have a matrix (57,3600,45), how can I create matrices with (3600,45)?
Is this what you want? k = some integer index squeeze(your_matrix(k,:,:))

8 days ago | 0

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Square root table without using arrays
You need to put the new line \n in appropriate places in your loops. In particular, you only need one new line \n printed once y...

8 days ago | 0

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Memory Size and Processor Speed
Yes you can run MATLAB on this. What tasks will you typically be using MATLAB for?

10 days ago | 0

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How to? - Complex numbers
E.g., for an anonymous function you need to give the input argument list first. E.g., for a generic derivative function that tak...

12 days ago | 0

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And/or between two 3d arrays
Do you mean this? sum(array1>250 & array2>170,3);

12 days ago | 0

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Function in Fortran to Funciton in Matlab
function result = F0(n,x) if( n<2 ) error('bad argument n in F0') end tox=2.0/x; bkm=F00(x); bk=F01(x); for j=1:n-1 ...

16 days ago | 1

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differentiating function & getting different answer
Perhaps you are shadowing the MATLAB function diff with a function of your own. Make sure diff is pointing to the MATLAB functio...

16 days ago | 0

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Invalid Syntax at '='.Possibly,a ),} or ] is missing at line 6 .
The { } formulation for blocking code is not valid MATLAB syntax. To fix this: Get rid of the open brace { Replace the close b...

17 days ago | 1

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Answered
use this vector and a mathematical expression to create the following vectors:
Yes. It works for me: >> x= [1, 2, 3, 4 ,5] x = 1 2 3 4 5 >> x1= x.*[1,128,243,64,5] x1 = 1 25...

22 days ago | 0

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Extracting matrix values for an algorithm
Something like this? xy = your n x 2 array n = size(xy,1); for k=1:n % run your algorithm here with x = xy(k,1) and y = ...

22 days ago | 1

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Answered
Basic power rule ((a^b)^c = a^(b*c)) does not work
This has been discussed in this forum before. Raising complex numbers to a power is a multi-valued operation. MATLAB picks one...

22 days ago | 1

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Is it possible to use logical indexing to specify between a number interval and include a value outside that interval.
E.g., Mask = ismember(str,[' ','a':'z','A':'Z']); Or using your method Mask = (65<=Ustr & Ustr<=90) | Ustr == 32;

23 days ago | 1

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BEGINNER PROBLEM: Trying to finish up an assignment but I am stuck with this error and am not sure how to fix
lab_total and assign_total and exam_total are all vectors, so the right hand side expression is a vector. You try to stuff that...

24 days ago | 1

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I have a problem with this ode45
I don't see anywhere in your code where you define i and j before using them as indexes into Phi0 and Z0, so they default to the...

24 days ago | 0

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Vector matrix multiplication with a condition
For later versions of MATLAB: c = all(A==B | A==2,2); For earlier versions: c = all(bsxfun(@eq,A,B) | A==2,2);

24 days ago | 0

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Can ode45 solve a ODE with space dependent parameters?
Yes. In general, if the derivative is a function of current state and time (even if there are vectors or matrices involved), the...

26 days ago | 2

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Is it possible to set rules for calculating permutations of column vectors?
Use the diff( ) function to calculate all of the permutations, and then count the number of valid ones. E.g., P = perms(1:i...

26 days ago | 1

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Answered
Get UNIX standard timestamp on MATLAB
You need to be careful about how you use the posixtime(t) function. From the documentation: "...If the time zone of t is not sp...

2 months ago | 2

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How can I determine the angle between two vectors in MATLAB?
This topic has been discussed many times on the Newsgroup forum ... if I looked hard enough I'm sure I could find several Roger ...

2 months ago | 3

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"To RESHAPE the number of elements must not change".This error occurs in line18.how to correct this error?
This expression is only going to work if size(a,1)*size(a,1) = numel(a): reshape(a,size(a,1),size(a,1),1); What are you trying...

2 months ago | 0

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Matlab crashes but Octave doesn't
What happens if you do the A\b differently? E.g., doing the LU decomposition manually and then backsolving yourself? Or doing pi...

2 months ago | 0

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R2018b real times complex multiplication
Probably related to the fact that complex variables changed to an interleaved storage format in R2018a. So my guess is this is w...

2 months ago | 2

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Write a function called WordProduct to calculate the alphabetic word product of a character vector.
Hints to get you started: Look at the upper( ) and lower( ) functions What happens if you subract 'a' or 'A' from your vector?...

2 months ago | 0

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Changing elements with a condition
clear X2 X3 [m,n] = size(X1); X2(2:m,2:n) = X1(1:m-1,1:n-1); X3(3:m,3:n) = X1(1:m-2,1:n-2);

2 months ago | 1

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Answered
I dont understand the vectors and element parts.
Typo. This j*y*(1) <-- Uses the full vector y times the scalar 1 should be this j*y(1) <-- Uses only the y(1) element

2 months ago | 0

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Answered
Efficient indexing with nested object and object arrays
Whether this works or not depends on what is in the properties, but have you tried simple concatenation on the rhs? [out] = [pa...

2 months ago | 0

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