5134 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.

Answered

mxCreateStructArray and mxCreateStructMatrix field name memory management

_"Are the field name character arrays copied before being stored internally?"_ Yes. Internally in the mxArray, the field name...

mxCreateStructArray and mxCreateStructMatrix field name memory management

_"Are the field name character arrays copied before being stored internally?"_ Yes. Internally in the mxArray, the field name...

1 day ago | 1

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Answered

I am trying to sort three numbers without using inbuilt functions.What is wrong with the function?

Two of your branches do not set all three output variables. E.g., if p(1)<=p(2) if p(1)<=p(3) small...

I am trying to sort three numbers without using inbuilt functions.What is wrong with the function?

Two of your branches do not set all three output variables. E.g., if p(1)<=p(2) if p(1)<=p(3) small...

1 day ago | 0

Answered

Definite Integrals With Answer

For Part A, the instructor may want the answer in terms of x, not t. E.g. syms x disp(int(40-2*t,0,x)) % <-- Or disp(s...

Definite Integrals With Answer

For Part A, the instructor may want the answer in terms of x, not t. E.g. syms x disp(int(40-2*t,0,x)) % <-- Or disp(s...

4 days ago | 0

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Answered

mexPrintf to standard error

Brute force? I can't think of another way to get at the MATLAB standard error printing. E.g., /* Includes ---------------...

mexPrintf to standard error

Brute force? I can't think of another way to get at the MATLAB standard error printing. E.g., /* Includes ---------------...

4 days ago | 0

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Answered

Making a matrix using colons or linspace working improperly within code

I suspect this is being caused by floating point round off error in the various calculations. Maybe just use a round in your lin...

Making a matrix using colons or linspace working improperly within code

I suspect this is being caused by floating point round off error in the various calculations. Maybe just use a round in your lin...

4 days ago | 0

| accepted

Answered

find closest pairs in two datetime arrays with unequal length

Are the arrays sorted? Using sorted arrays, one could come up with a stepping algorithm. E.g., if you know that t2(k) < t1(i) ...

find closest pairs in two datetime arrays with unequal length

Are the arrays sorted? Using sorted arrays, one could come up with a stepping algorithm. E.g., if you know that t2(k) < t1(i) ...

7 days ago | 0

Answered

Taylor and Euler Method for ODE

MATLAB is a 0-based indexing language. So you can't have y(0) in your code. It will need to start at y(1). y(1)= -0.25; ...

Taylor and Euler Method for ODE

MATLAB is a 0-based indexing language. So you can't have y(0) in your code. It will need to start at y(1). y(1)= -0.25; ...

7 days ago | 0

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Posted

reading and writing matrices from c++

snip) (snip) Actually, what I meant was how are you doing the compile itself? From within MATLAB or from within Visual Studi...

7 days ago | 215 views

Answered

Coversion of visual c to matlab line

Rather than converting the code, you might consider a mex solution: https://www.mathworks.com/help/matlab/programming-interfa...

Coversion of visual c to matlab line

Rather than converting the code, you might consider a mex solution: https://www.mathworks.com/help/matlab/programming-interfa...

7 days ago | 0

Answered

How to pass parameters?

Not sure if this is what you want, but just pass them in: dX = -13.925*A*B*C*x + f(t,A,B,C); : function fval =...

How to pass parameters?

Not sure if this is what you want, but just pass them in: dX = -13.925*A*B*C*x + f(t,A,B,C); : function fval =...

7 days ago | 1

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Posted

reading and writing messages from c++

Please tell us the MATLAB version you are using and the operating system. Also post the exact code you are using to do the comp...

7 days ago | 215 views

Answered

Trying to graph each iteration of the for loop

You are plotting p(1,:) in the loop, but this never changes in the loop. Did you mean to plot pdot instead? E.g., plot(t,pd...

Trying to graph each iteration of the for loop

You are plotting p(1,:) in the loop, but this never changes in the loop. Did you mean to plot pdot instead? E.g., plot(t,pd...

8 days ago | 0

Answered

4-D array to 3-D array

E.g., x = your 304 * 448 * 37 * 12 array y = reshape(x,304,448,37*12); Another possibility if you want those last two...

4-D array to 3-D array

E.g., x = your 304 * 448 * 37 * 12 array y = reshape(x,304,448,37*12); Another possibility if you want those last two...

8 days ago | 0

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Answered

Error with matrix dimensions depending on which version of matlab i use.

Guessing that your friends are running R2016b and you are running an earlier version. In R2016b dimension mismatches such as thi...

Error with matrix dimensions depending on which version of matlab i use.

Guessing that your friends are running R2016b and you are running an earlier version. In R2016b dimension mismatches such as thi...

8 days ago | 2

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Answered

Problem converting cell to string

If the individual cells can have more than two elements, e.g., U={[1,4],[1,5],[1,6],[2,4],[2,5],[2,6],[3,4,5],[3,5],[3,6,9]...

Problem converting cell to string

If the individual cells can have more than two elements, e.g., U={[1,4],[1,5],[1,6],[2,4],[2,5],[2,6],[3,4,5],[3,5],[3,6,9]...

8 days ago | 0

Answered

Create a new field in a structure

Not sure if this is what you are really asking: mystruct.field1 = rand(1,3); % <-- Create a structure with field named fie...

Create a new field in a structure

Not sure if this is what you are really asking: mystruct.field1 = rand(1,3); % <-- Create a structure with field named fie...

8 days ago | 0

Answered

Weird!!!! Extremely simple question!! Can't assign values to first row of a sparse matrix, please help.

Typo. You used a small case 's' in that first row assignment. Change that to an upper case 'S' and everything will be as expecte...

Weird!!!! Extremely simple question!! Can't assign values to first row of a sparse matrix, please help.

Typo. You used a small case 's' in that first row assignment. Change that to an upper case 'S' and everything will be as expecte...

9 days ago | 1

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Answered

A Few Key Concepts to Take From One Complete Program and Apply to Another Very Similar Second Computer Program from an Exponential Distribution with Lambda Function Applied..

I _*think*_ your question is how to generate exponential(lambda) random numbers. If so, you can get them from uniform(0,1) numbe...

A Few Key Concepts to Take From One Complete Program and Apply to Another Very Similar Second Computer Program from an Exponential Distribution with Lambda Function Applied..

I _*think*_ your question is how to generate exponential(lambda) random numbers. If so, you can get them from uniform(0,1) numbe...

9 days ago | 0

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Answered

How do I isolate a letter in some equation?

symvar is probably what you are looking for. E.g., >> eqn = '2=2*log(x).^2'; >> symvar(eqn) ans = 'x' EDIT...

How do I isolate a letter in some equation?

symvar is probably what you are looking for. E.g., >> eqn = '2=2*log(x).^2'; >> symvar(eqn) ans = 'x' EDIT...

9 days ago | 1

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Answered

How to limit user input to only one character?

Maybe this FEX submission by Jos is close to what you want: http://www.mathworks.com/matlabcentral/fileexchange/7465-getkey ...

How to limit user input to only one character?

Maybe this FEX submission by Jos is close to what you want: http://www.mathworks.com/matlabcentral/fileexchange/7465-getkey ...

9 days ago | 0

Answered

Matrix indexing multiple rows

x = your matrix result = x([2:4,5:8],:); % <-- pick off rows 2-4 and 5-8 Of course, the 2:4 and 5:8 could have been com...

Matrix indexing multiple rows

x = your matrix result = x([2:4,5:8],:); % <-- pick off rows 2-4 and 5-8 Of course, the 2:4 and 5:8 could have been com...

9 days ago | 0

Answered

I need to compare two large arrays of data. Running is too slow, it takes 5 days to run the script below. Is it possible to run the script in less time? As?

Not a complete solution, but for starters I would suggest the following: Pull all of the data copying you do that does not de...

I need to compare two large arrays of data. Running is too slow, it takes 5 days to run the script below. Is it possible to run the script in less time? As?

Not a complete solution, but for starters I would suggest the following: Pull all of the data copying you do that does not de...

9 days ago | 0

Answered

How to repeat a for loop n times

Is this all you are trying to do? n = number of times to repeat the loop States = zeros(size(N,1)); for k=1:n ...

How to repeat a for loop n times

Is this all you are trying to do? n = number of times to repeat the loop States = zeros(size(N,1)); for k=1:n ...

9 days ago | 0

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Answered

i want to make a for loop that goes like this for a=0:1:180 && 179:-1:-180 but it is not possible in matlab, any ideas how to do it?

It is not clear to me what you really want. Maybe this? for a=[0:1:180,179:-1:-180] % whatever end

i want to make a for loop that goes like this for a=0:1:180 && 179:-1:-180 but it is not possible in matlab, any ideas how to do it?

It is not clear to me what you really want. Maybe this? for a=[0:1:180,179:-1:-180] % whatever end

9 days ago | 0

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Answered

need a help using loop

You have learned the hard way one of the first lessons of good programming practice ... don't create a bunch of variables with t...

need a help using loop

You have learned the hard way one of the first lessons of good programming practice ... don't create a bunch of variables with t...

9 days ago | 0

Responded

Re: Uncomment shortcut on Matlab

Does Ctrl-t work to uncomment a block of code? (And Ctrl-r for commenting) James Tursa

10 days ago | 212 views

Answered

How to confirm user input is a word based on ascii table?

Like this? prompt = 'Enter word '; while( true ) answer = input(prompt, 's'); if( all(ismember(answer,'AB...

How to confirm user input is a word based on ascii table?

Like this? prompt = 'Enter word '; while( true ) answer = input(prompt, 's'); if( all(ismember(answer,'AB...

10 days ago | 0

Answered

Question about machine epsilon

The short answer is that the result is rounded. How this rounding takes place is going to depend on the rounding modes available...

Question about machine epsilon

The short answer is that the result is rounded. How this rounding takes place is going to depend on the rounding modes available...

11 days ago | 2

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Answered

Improve efficiency of backslash operator for sparse matrices

You might find something in Tim Davis FEX submissions that would help: http://www.mathworks.com/matlabcentral/fileexchange/?t...

Improve efficiency of backslash operator for sparse matrices

You might find something in Tim Davis FEX submissions that would help: http://www.mathworks.com/matlabcentral/fileexchange/?t...

11 days ago | 0

Answered

matlab code to make values of an array in specific ranges(index positions) equal to zero

for k=1:numel(start_index_positions) d(start_index_positions(k):end_index_positions(k)) = 0; end

matlab code to make values of an array in specific ranges(index positions) equal to zero

for k=1:numel(start_index_positions) d(start_index_positions(k):end_index_positions(k)) = 0; end

11 days ago | 0