James Tursa
2 914 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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Contribute at least one answer each month for 36 consecutive months
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Awarded to James Tursa on 26 Feb 2012
How to loop through all rows using a for loop
I will get you started: patients = the variable that has all of the patient information for k=1:_______ <-- you fill this in ...
ungefär 13 timmar ago | 0
Help with learning indexing
x is size 2x3, so the 'end' in the 2nd index position is 3. Then just do the math (3-1)/2 = 2/2 = 1 so x(2,(end-1)/2) = x(2,1)...
ungefär 14 timmar ago | 0
Cross Product of an Array
M = your 3xN matrix v = your 3x1 vector result = cross(M,repmat(v,1,size(M,2)));
ungefär 20 timmar ago | 0
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i need solve m*d2x/dt2 + c*dx/dt + k*x= 0 with matlab and I have encountered an error Undefined function or variable 't'. please help me
Is this code all together in one file as written above? You need to have your driver code (the code that calls ode45) first, an...
ungefär 23 timmar ago | 0
How top stop for loop if value is reached
if( norm(X(c+1,:)-X(c,:)) < some_tolerance ) break; end or perhaps if( all(abs(X(c+1,:)-X(c,:))) < some_tolerance ) ...
4 dagar ago | 0
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2 degrees of freedom mass-spring system
In this line dy=[y(2);y(4);dy(3);-inv(M)*K*y]; looks like M and K are both 2x2 but y is 4x1, hence the error. Also, your argu...
5 dagar ago | 0
Fourth Order Runge Kutta for Systems
This line does not have the rhs state syntax correct: y_vals(i+1,:) = y_vals(i) + (k_1+2*(k_2+k_3)+k_4)/6*h; It should be thi...
5 dagar ago | 0
Vectorize many matrix multiplications using the third dimension
See this link: https://www.mathworks.com/matlabcentral/answers/456711-how-can-i-do-matrix-multiplication-on-sets-of-data-in-an-...
6 dagar ago | 1
i want to plot x and y for ODE45 function
This line doesn't look correct: dy(1) = x(2); The first agument x in the derivative function is the independent variable and a...
6 dagar ago | 1
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How can I do matrix multiplication on sets of data in an array without looping?
First, some basic data storage advice. When you have multiple matrices stored in a larger matrix or array, it is usually best to...
7 dagar ago | 1
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Help Converting C++ to MATLAB.
Probably easiest is just to do it by hand one line at a time. Replace the control syntax with its MATLAB counterpart, and add 1...
8 dagar ago | 0
Second Order ODE with Runge Kutta 3 "K's problem"
You are using the same k's for x1 and x2, which is incorrect. That is, you are using f2( ) to calculate the k's, but these shoul...
8 dagar ago | 0
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Nonscalar arrays of function handles are not allowed; use cell arrays instead error, not sure what it means / how to fix it
You are simply using the wrong syntax for what you really want. It should be something like this instead: %v[1] = x %v[2] = y...
12 dagar ago | 0
What function returns (as an integer) the number of bits in a data type or class, e.g. returns 16 for 'int16' or 'uint16' variables, 32 (or whatever) for 'float' types, etc.?
I think everything that MATLAB runs on currently uses IEEE single and double floating point formats. And the signed integer for...
12 dagar ago | 0
To Stupid for Matrix Loop
Do you mean simply this? for i=x for j=y IMG(i,j) = pixfilter(IMG,i,j); end end
12 dagar ago | 0
How do i write an input statement asking the user to enter their birthdate as a matrix with entries of month,day, year?
If the user follows instructions, birthdate will be a vector of three numbers, so you need the format string to print out three ...
13 dagar ago | 1
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Solving questions related to taylor series expansion
You need to compare the absolute value of the term to your tolerance. Remember, some of the terms are negative. while abs(term(...
13 dagar ago | 0
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Recursion for Unnesting 1x1 Cell Array
Are you sure it is a single quote char string 'example' and not a double quote string "another_example"? What is the actual err...
13 dagar ago | 0
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sum command giving ridiculous answer
It could be you are comparing apples to oranges. The actual numbers probably have more than four digits that are not being displ...
13 dagar ago | 2
Why am I getting "Undefined function or variable" when I use an exponential in the function?
There is no "I" variable in your code. Hence the error.
13 dagar ago | 0
Generate 500 numbers using probability density functions
r = rand(1,500); Use the r values as an indicator of which distribution f or g to draw from. For those r < 0.4, generate normal...
13 dagar ago | 1
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Pre-locating an array
Numeric arrays must be rectangular. You cannot have different dimensions for different slices. To get that behavior you would n...
13 dagar ago | 0
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How to find Matlab version to be used in the mex file header
Version info for mex routines can be found in this FEX submission: https://www.mathworks.com/matlabcentral/fileexchange/67016-c...
13 dagar ago | 1
How do I reorder a 3D matrix in a specific way?
There's got to be a simpler way, but here goes p = permute(MeanV,[2 1 3]); result = reshape(cat(3,p(:,1,:),p(:,2,:),p(:,3,:)),...
14 dagar ago | 0
Index exceeds matrix dimensions
You don't index wE in your loop when you are doing the iterations, so each iteration overwrites the previous iteration. Looks li...
14 dagar ago | 0
Column-wise inexing of matrix
One way that is scalable and matches your example: A(indx + (0:size(indx,2)-1)*size(A,1)) This uses implicit expansion. On ear...
14 dagar ago | 1
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Multiply each column of a matrix by another matrix
Another way: C = sqrt(sum(E.*(J*E))); For the sizes involved, you probably won't see any significant timing differences betwee...
14 dagar ago | 1
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What does zeros(2,3,4) mean?
It creates a double array of dimensions 2 x 3 x 4 filled with 0's. doc zeros
15 dagar ago | 1