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  • How to reshape matrices in Mathematica

    - by speciousfool
    When manipulating matrices it is often convenient to change their shape. For instance, to turn an N x M sized matrix into a vector of length N X M. In MATLAB a reshape function exists: RESHAPE(X,M,N) returns the M-by-N matrix whose elements are taken columnwise from X. An error results if X does not have M*N elements. In the case of converting between a matrix and vector I can use the Mathematica function Flatten which takes advantage of Mathematica's nested list representation for matrices. As a quick example, suppose I have a matrix X: With Flatten[X] I can get the vector {1,2,3,...,16}. But what would be far more useful is something akin to applying Matlab's reshape(X,2,8) which would result in the following Matrix: This would allow creation of arbitrary matrices as long as the dimensions equal N*M. As far as I can tell, there isn't anything built in which makes me wonder if someone hasn't coded up a Reshape function of their own.

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  • Marshal struct to unmanaged array

    - by Pedro
    Hi guys, I have a C# struct to represent a cartesian vector, something like this: public struct Vector { private double x; private double y; private double z; //Some properties/methods } Now I have an unmanaged C dll that I need to call with P/Invoke. Some methods expect a double[3] parameter. The unmanaged C signature is something like void Cross(double a[3], double b[3], double c[3]); Is there any way to set up a P/Invoke signature so I can pass instances of my Vector struct and marshal them transparently to unmanaged double[3]? I would also need bidirectional marshaling as the unmanaged function needs to write the output to the argument array, so I guess I would need to marshal as LpArray. Any ideas? Thanks Pedro

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  • Question on multi-probe Local Sensitive Hashing

    - by Yijinsei
    Hey guys sorry to be asking this kind noob question, but because I really need some guidance on how to use Multi probe LSH pretty urgently, so I did not do much research myself. I realize there is a lib call LSHKIT available that implemented that algorithm, but I have trouble trying to figure out how to use it. Right now, I have a few thousand feature vector 296 dimension, each representing an image. The vector is used to query an user input image, to retrieve the most similar image. The method I used to derive the distance between vector is euclidean distance. I know this might be a rather noob question, but do you guys have knowledge on how should i implement multi probe LSH? I am really very grateful to any answer or response.

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  • Java Swing GUI exception - Exception in thread "AWT-EventQueue-0" java.util.NoSuchElementException:

    - by rgksugan
    I get this exception when i run my application. I dont have any idea what is going wrong here. Can someone help please. Exception in thread "AWT-EventQueue-0" java.util.NoSuchElementException: Vector Enumeration at java.util.Vector$1.nextElement(Vector.java:305) at javax.swing.plaf.basic.BasicTableHeaderUI.getPreferredSize(BasicTableHeaderUI.java:778) at javax.swing.JComponent.getPreferredSize(JComponent.java:1634) at javax.swing.ViewportLayout.preferredLayoutSize(ViewportLayout.java:78) at java.awt.Container.preferredSize(Container.java:1599) at java.awt.Container.getPreferredSize(Container.java:1584) at javax.swing.JComponent.getPreferredSize(JComponent.java:1636) at javax.swing.ScrollPaneLayout.layoutContainer(ScrollPaneLayout.java:702) at java.awt.Container.layout(Container.java:1421) at java.awt.Container.doLayout(Container.java:1410) at java.awt.Container.validateTree(Container.java:1507) at java.awt.Container.validate(Container.java:1480) at javax.swing.RepaintManager.validateInvalidComponents(RepaintManager.java:669) at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(SystemEventQueueUtilities.java:124) at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209) at java.awt.EventQueue.dispatchEvent(EventQueue.java:597) at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269) at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161) at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

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  • How to handle value types when embedding IronPython in C#?

    - by kloffy
    There is a well known issue when it comes to using .NET value types in IronPython. This has recently caused me a headache when trying to use Python as an embedded scripting language in C#. The problem can be summed up as follows: Given a C# struct such as: struct Vector { public float x; public float y; } And a C# class such as: class Object { public Vector position; } The following will happen in IronPython: obj = Object() print obj.position.x # prints ‘0’ obj.position.x = 1 print obj.position.x # still prints ‘0’ As the article states, this means that value types are mostly immutable. However, this is a problem as I was planning on using a vector library that is implemented as seen above. Are there any workarounds for working with existing libraries that rely on value types? Modifying the library would be the very last resort, but I'd rather avoid that.

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  • Compile error C++: could not deduce template argument for 'T'

    - by OneShot
    I'm trying to read binary data to load structs back into memory so I can edit them and save them back to the .dat file. readVector() attempts to read the file, and return the vectors that were serialized. But i'm getting this compile error when I try and run it. What am I doing wrong with my templates? ***** EDIT ************** Code: // Project 5.cpp : main project file. #include "stdafx.h" #include <iostream> #include <fstream> #include <string> #include <vector> #include <algorithm> using namespace System; using namespace std; #pragma hdrstop int checkCommand (string line); template<typename T> void writeVector(ofstream &out, const vector<T> &vec); template<typename T> vector<T> readVector(ifstream &in); struct InventoryItem { string Item; string Description; int Quantity; int wholesaleCost; int retailCost; int dateAdded; } ; int main(void) { cout << "Welcome to the Inventory Manager extreme! [Version 1.0]" << endl; ifstream in("data.dat"); vector<InventoryItem> structList; readVector<InventoryItem>( in ); while (1) { string line = ""; cout << endl; cout << "Commands: " << endl; cout << "1: Add a new record " << endl; cout << "2: Display a record " << endl; cout << "3: Edit a current record " << endl; cout << "4: Exit the program " << endl; cout << endl; cout << "Enter a command 1-4: "; getline(cin , line); int rValue = checkCommand(line); if (rValue == 1) { cout << "You've entered a invalid command! Try Again." << endl; } else if (rValue == 2){ cout << "Error calling command!" << endl; } else if (!rValue) { break; } } system("pause"); return 0; } int checkCommand (string line) { int intReturn = atoi(line.c_str()); int status = 3; switch (intReturn) { case 1: break; case 2: break; case 3: break; case 4: status = 0; break; default: status = 1; break; } return status; } template<typename T> void writeVector(ofstream &out, const vector<T> &vec) { out << vec.size(); for(vector<T>::const_iterator i = vec.begin(); i != vec.end(); i++) { out << *i; } } ostream& operator<<(std::ostream &strm, const InventoryItem &i) { return strm << i.Item << " (" << i.Description << ")"; } template<typename T> vector<T> readVector(ifstream &in) { size_t size; in >> size; vector<T> vec; vec.reserve(size); for(int i = 0; i < size; i++) { T tmp; in >> tmp; vec.push_back(tmp); } return vec; } Compiler errors: 1>------ Build started: Project: Project 5, Configuration: Debug Win32 ------ 1>Compiling... 1>Project 5.cpp 1>.\Project 5.cpp(124) : warning C4018: '<' : signed/unsigned mismatch 1> .\Project 5.cpp(40) : see reference to function template instantiation 'std::vector<_Ty> readVector<InventoryItem>(std::ifstream &)' being compiled 1> with 1> [ 1> _Ty=InventoryItem 1> ] 1>.\Project 5.cpp(127) : error C2679: binary '>>' : no operator found which takes a right-hand operand of type 'InventoryItem' (or there is no acceptable conversion) 1> C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\include\istream(1144): could be 'std::basic_istream<_Elem,_Traits> &std::operator >><std::char_traits<char>>(std::basic_istream<_Elem,_Traits> &,signed char *)' 1> with 1> [ 1> _Elem=char, 1> _Traits=std::char_traits<char> 1> ] 1> C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\include\istream(1146): or 'std::basic_istream<_Elem,_Traits> &std::operator >><std::char_traits<char>>(std::basic_istream<_Elem,_Traits> &,signed char &)' 1> with 1> [ 1> _Elem=char, 1> _Traits=std::char_traits<char> 1> ] 1> C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\include\istream(1148): or 'std::basic_istream<_Elem,_Traits> &std::operator >><std::char_traits<char>>(std::basic_istream<_Elem,_Traits> &,unsigned char *)' 1> with 1> [ 1> _Elem=char, 1> _Traits=std::char_traits<char> 1> ] 1> C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\include\istream(1150): or 'std::basic_istream<_Elem,_Traits> &std::operator >><std::char_traits<char>>(std::basic_istream<_Elem,_Traits> &,unsigned char &)' 1> with 1> [ 1> _Elem=char, 1> _Traits=std::char_traits<char> 1> ] 1> C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\include\istream(155): or 'std::basic_istream<_Elem,_Traits> &std::basic_istream<_Elem,_Traits>::operator >>(std::basic_istream<_Elem,_Traits> &(__cdecl *)(std::basic_istream<_Elem,_Traits> &))' 1> with 1> [ 1> _Elem=char, 1> _Traits=std::char_traits<char> 1> ] 1> C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\include\istream(161): or 'std::basic_istream<_Elem,_Traits> &std::basic_istream<_Elem,_Traits>::operator >>(std::basic_ios<_Elem,_Traits> &(__cdecl *)(std::basic_ios<_Elem,_Traits> &))' 1> with 1> [ 1> _Elem=char, 1> _Traits=std::char_traits<char> 1> ] 1> C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\include\istream(168): or 'std::basic_istream<_Elem,_Traits> &std::basic_istream<_Elem,_Traits>::operator >>(std::ios_base &(__cdecl *)(std::ios_base &))' 1> with 1> [ 1> _Elem=char, 1> _Traits=std::char_traits<char> 1> ] 1> C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\include\istream(175): or 'std::basic_istream<_Elem,_Traits> &std::basic_istream<_Elem,_Traits>::operator >>(std::_Bool &)' 1> with 1> [ 1> _Elem=char, 1> _Traits=std::char_traits<char> 1> ] 1> C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\include\istream(194): or 'std::basic_istream<_Elem,_Traits> &std::basic_istream<_Elem,_Traits>::operator >>(short &)' 1> with 1> [ 1> _Elem=char, 1> _Traits=std::char_traits<char> 1> ] 1> C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\include\istream(228): or 'std::basic_istream<_Elem,_Traits> &std::basic_istream<_Elem,_Traits>::operator >>(unsigned short &)' 1> with 1> [ 1> _Elem=char, 1> _Traits=std::char_traits<char> 1> ] 1> C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\include\istream(247): or 'std::basic_istream<_Elem,_Traits> &std::basic_istream<_Elem,_Traits>::operator >>(int &)' 1> with 1> [ 1> _Elem=char, 1> _Traits=std::char_traits<char> 1> ] 1> C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\include\istream(273): or 'std::basic_istream<_Elem,_Traits> &std::basic_istream<_Elem,_Traits>::operator >>(unsigned int &)' 1> with 1> [ 1> _Elem=char, 1> _Traits=std::char_traits<char> 1> ] 1> C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\include\istream(291): or 'std::basic_istream<_Elem,_Traits> &std::basic_istream<_Elem,_Traits>::operator >>(long &)' 1> with 1> [ 1> _Elem=char, 1> _Traits=std::char_traits<char> 1> ] 1> C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\include\istream(309): or 'std::basic_istream<_Elem,_Traits> &std::basic_istream<_Elem,_Traits>::operator >>(__w64 unsigned long &)' 1> with 1> [ 1> _Elem=char, 1> _Traits=std::char_traits<char> 1> ] 1> C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\include\istream(329): or 'std::basic_istream<_Elem,_Traits> &std::basic_istream<_Elem,_Traits>::operator >>(__int64 &)' 1> with 1> [ 1> _Elem=char, 1> _Traits=std::char_traits<char> 1> ] 1> C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\include\istream(348): or 'std::basic_istream<_Elem,_Traits> &std::basic_istream<_Elem,_Traits>::operator >>(unsigned __int64 &)' 1> with 1> [ 1> _Elem=char, 1> _Traits=std::char_traits<char> 1> ] 1> C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\include\istream(367): or 'std::basic_istream<_Elem,_Traits> &std::basic_istream<_Elem,_Traits>::operator >>(float &)' 1> with 1> [ 1> _Elem=char, 1> _Traits=std::char_traits<char> 1> ] 1> C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\include\istream(386): or 'std::basic_istream<_Elem,_Traits> &std::basic_istream<_Elem,_Traits>::operator >>(double &)' 1> with 1> [ 1> _Elem=char, 1> _Traits=std::char_traits<char> 1> ] 1> C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\include\istream(404): or 'std::basic_istream<_Elem,_Traits> &std::basic_istream<_Elem,_Traits>::operator >>(long double &)' 1> with 1> [ 1> _Elem=char, 1> _Traits=std::char_traits<char> 1> ] 1> C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\include\istream(422): or 'std::basic_istream<_Elem,_Traits> &std::basic_istream<_Elem,_Traits>::operator >>(void *&)' 1> with 1> [ 1> _Elem=char, 1> _Traits=std::char_traits<char> 1> ] 1> C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\include\istream(441): or 'std::basic_istream<_Elem,_Traits> &std::basic_istream<_Elem,_Traits>::operator >>(std::basic_streambuf<_Elem,_Traits> *)' 1> with 1> [ 1> _Elem=char, 1> _Traits=std::char_traits<char> 1> ] 1> while trying to match the argument list '(std::ifstream, InventoryItem)' 1>Build log was saved at "file://c:\Users\Owner\Documents\Visual Studio 2008\Projects\Project 5\Project 5\Debug\BuildLog.htm" 1>Project 5 - 1 error(s), 1 warning(s) ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ========== Oh my god...I fixed that error I think and now I got another one. Will you PLEASE just help me on this one too! What the heck does this mean ??

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  • Howto project a planar polygon on a plane in 3d-space

    - by sum1stolemyname
    I want to project my Polygon along a vector to a plane in 3d Space. I would preferably use a single transformation matrix to do this, but I don't know how to build a matrix of this kind. Given the plane's parameters (ax+by+cz+d), the world coordinates of my Polygon. As stated in the the headline, all vertices of my polygon lie in another plane. the direction vector along which to project my Polygon (currently the polygon's plane's normal vector) goal -a 4x4 transformation matrix which performs the required projection, or some insight on how to construct one myself

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  • OpenLayers .containsPoint after pan

    - by Adrian
    I've seem to have hit a bug or i have overlooked something. I written some code that enumerates through all the vector features on a OpenLayers Vector layer - to check if the mouse is inside a vector feature - if so then it displays some info based on the feature. I had to write my own methods to do this because the existing OpenLayers Controls( select etc) stop after finding a feature under the mouse, and i the possibility of several features being stacked on top of one another. My problem is that the .containsPoint method seems to be using coords from before a 'pan'. After zooming in or out the geometry seems to be in the right place and .containsPoint is works correctly when I wave the mouse over the map. Do I need to do something after the map has been panned to update something( feature's geometry)

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  • Binning a numeric variable in R

    - by McPeterson
    I have a vector X that contains positive numbers that I want to bin/discretize. For this vector, I want the numbers [0, 10) to show up just as they exist in the vector, but numbers [10,∞) to be 10+. I'm using: x <- c(0,1,3,4,2,4,2,5,43,432,34,2,34,2,342,3,4,2) binned.x <- as.factor(ifelse(x > 10,"10+",x)) but this feels klugey to me. Does anyone know a better solution or a different approach? mcpeterson

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  • MinGW and "declaration does not declare anything"

    - by Bob Somers
    I'm working on converting a Linux project of mine to compile on Windows using MinGW. It compiles and runs just fine on Linux, but when I attempt to compile it with MinGW it bombs out with the following error message: camera.h:11: error: declaration does not declare anything camera.h:12: error: declaration does not declare anything I'm kind of baffled why this is happening, because I'm using the same version of g++ (4.4) on both Linux and Windows (via MinGW). The contents of camera.h is absurdly simple. Here's the code. It's choking on lines 11 and 12 where float near; and float far; are defined. #include "Vector.h" #ifndef _CAMERA_H_ #define _CAMERA_H_ class Camera{ public: Vector eye; Vector lookAt; float fov; float near; float far; }; #endif Thanks for your help.

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  • MinGW and "delcaration does not declare anything"

    - by Bob Somers
    I'm working on converting a Linux project of mine to compile on Windows using MinGW. It compiles and runs just fine on Linux, but when I attempt to compile it with MinGW it bombs out with the following error message: camera.h:11: error: declaration does not declare anything camera.h:12: error: declaration does not declare anything I'm kind of baffled why this is happening, because I'm using the same version of g++ (4.4) on both Linux and Windows (via MinGW). The contents of camera.h is absurdly simple. Here's the code. It's choking on lines 11 and 12 where float near; and float far; are defined. #include "Vector.h" #ifndef _CAMERA_H_ #define _CAMERA_H_ class Camera{ public: Vector eye; Vector lookAt; float fov; float near; float far; }; #endif Thanks for your help.

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  • Access violation using LocalAlloc()

    - by PaulH
    I have a Visual Studio 2008 Windows Mobile 6 C++ application that is using an API that requires the use of LocalAlloc(). To make my life easier, I created an implementation of a standard allocator that uses LocalAlloc() internally: /// Standard library allocator implementation using LocalAlloc and LocalReAlloc /// to create a dynamically-sized array. /// Memory allocated by this allocator is never deallocated. That is up to the /// user. template< class T, int max_allocations > class LocalAllocator { public: typedef T value_type; typedef size_t size_type; typedef ptrdiff_t difference_type; typedef T* pointer; typedef const T* const_pointer; typedef T& reference; typedef const T& const_reference; pointer address( reference r ) const { return &r; }; const_pointer address( const_reference r ) const { return &r; }; LocalAllocator() throw() : c_( NULL ) { }; /// Attempt to allocate a block of storage with enough space for n elements /// of type T. n>=1 && n<=max_allocations. /// If memory cannot be allocated, a std::bad_alloc() exception is thrown. pointer allocate( size_type n, const void* /*hint*/ = 0 ) { if( NULL == c_ ) { c_ = LocalAlloc( LPTR, sizeof( T ) * n ); } else { HLOCAL c = LocalReAlloc( c_, sizeof( T ) * n, LHND ); if( NULL == c ) LocalFree( c_ ); c_ = c; } if( NULL == c_ ) throw std::bad_alloc(); return reinterpret_cast< T* >( c_ ); }; /// Normally, this would release a block of previously allocated storage. /// Since that's not what we want, this function does nothing. void deallocate( pointer /*p*/, size_type /*n*/ ) { // no deallocation is performed. that is up to the user. }; /// maximum number of elements that can be allocated size_type max_size() const throw() { return max_allocations; }; private: /// current allocation point HLOCAL c_; }; // class LocalAllocator My application is using that allocator implementation in a std::vector< #define MAX_DIRECTORY_LISTING 512 std::vector< WIN32_FIND_DATA, LocalAllocator< WIN32_FIND_DATA, MAX_DIRECTORY_LISTING > > file_list; WIN32_FIND_DATA find_data = { 0 }; HANDLE find_file = ::FindFirstFile( folder.c_str(), &find_data ); if( NULL != find_file ) { do { // access violation here on the 257th item. file_list.push_back( find_data ); } while ( ::FindNextFile( find_file, &find_data ) ); ::FindClose( find_file ); } // data submitted to the API that requires LocalAlloc()'d array of WIN32_FIND_DATA structures SubmitData( &file_list.front() ); On the 257th item added to the vector<, the application crashes with an access violation: Data Abort: Thread=8e1b0400 Proc=8031c1b0 'rapiclnt' AKY=00008001 PC=03f9e3c8(coredll.dll+0x000543c8) RA=03f9ff04(coredll.dll+0x00055f04) BVA=21ae0020 FSR=00000007 First-chance exception at 0x03f9e3c8 in rapiclnt.exe: 0xC0000005: Access violation reading location 0x01ae0020. LocalAllocator::allocate is called with an n=512 and LocalReAlloc() succeeds. The actual Access Violation exception occurs within the std::vector< code after the LocalAllocator::allocate call: 0x03f9e3c8 0x03f9ff04 > MyLib.dll!stlp_std::priv::__copy_trivial(const void* __first = 0x01ae0020, const void* __last = 0x01b03020, void* __result = 0x01b10020) Line: 224, Byte Offsets: 0x3c C++ MyLib.dll!stlp_std::vector<_WIN32_FIND_DATAW,LocalAllocator<_WIN32_FIND_DATAW,512> >::_M_insert_overflow(_WIN32_FIND_DATAW* __pos = 0x01b03020, _WIN32_FIND_DATAW& __x = {...}, stlp_std::__true_type& __formal = {...}, unsigned int __fill_len = 1, bool __atend = true) Line: 112, Byte Offsets: 0x5c C++ MyLib.dll!stlp_std::vector<_WIN32_FIND_DATAW,LocalAllocator<_WIN32_FIND_DATAW,512> >::push_back(_WIN32_FIND_DATAW& __x = {...}) Line: 388, Byte Offsets: 0xa0 C++ MyLib.dll!Foo(unsigned long int cbInput = 16, unsigned char* pInput = 0x01a45620, unsigned long int* pcbOutput = 0x1dabfbbc, unsigned char** ppOutput = 0x1dabfbc0, IRAPIStream* __formal = 0x00000000) Line: 66, Byte Offsets: 0x1e4 C++ If anybody can point out what I may be doing wrong, I would appreciate it. Thanks, PaulH

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  • How to create a string array in matlab?

    - by aduric
    I would like to pass a vector of strings from C++ to matlab. I have tried using the functions available such as mxCreateCharMatrixFromStrings but it doesn't give me the correct behavior. So, I have something like this: void mexFunction( int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[]) { vector<string> stringVector; stringVector.push_back("string 1"); stringVector.push_back("string 2"); //etc... The problem is how do I get this vector to the matlab environment? plhs[0] = ??? My goal is to be able to run: >> [strings] = MyFunc(...) >> strings(1) = 'string 1'

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  • Suggest changes to make the time a function of input size

    - by KB
    Vector v; int i=0; while(i!=999) { cini; v.push_back(i); } Time taken by this piece of code could vary when the number of inputs vary. Since vector would take amortized time for new allocation. Even for same size the program at different times could take different time. Suggest changes (e.g. use list instead of vector), which makes the time a function of number of inputs.

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  • Collision detection by sliding against a plane in XNA

    - by Bevin
    Hello, I am attempting to engineer a collision detection algorithm for a custom Minecraft client I'm making. Basically, the entire world is made up of cubes, and the player (or camera) needs to be able to stand on and move against these cubes. The result I want is illustrated in this image: The green line is the player's movement vector. When the player is brushing up against a plane of one of the cubes, I want the vector to change to one that is perpendicular with the plane. The vector should, however, keep all of it's velocity in the plane's direction, yet lose all velocity towards the plane. I hope I've made my question clear. What is the best and most efficient way to implement a collision detection system like this? Also, will a system like this allow for a simple gravity component?

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  • Distance between numpy arrays, columnwise

    - by Jaapsneep
    I have 2 arrays in 2D, where the column vectors are feature vectors. One array is of size F x A, the other of F x B, where A << B. As an example, for A = 2 and F = 3 (B can be anything): arr1 = np.array( [[1, 4], [2, 5], [3, 6]] ) arr2 = np.array( [[1, 4, 7, 10, ..], [2, 5, 8, 11, ..], [3, 6, 9, 12, ..]] ) I want to calculate the distance between arr1 and a fragment of arr2 that is of equal size (in this case, 3x2), for each possible fragment of arr2. The column vectors are independent of each other, so I believe I should calculate the distance between each column vector in arr1 and a collection of column vectors ranging from i to i + A from arr2 and take the sum of these distances (not sure though). Does numpy offer an efficient way of doing this, or will I have to take slices from the second array and, using another loop, calculate the distance between each column vector in arr1 and the corresponding column vector in the slice?

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  • Templates --> How to decipher, decide if necessary and create?

    - by ML
    Hi All, I have a few classes in a project that I inherited that are really old, last I knew they compiled with CodeWarrior 8. I am not in XCode 3.2 Here is an example of what I struggle with: template <class registeredObject> typename std::vector<registeredObject>::iterator FxRegistry<registeredObject>::begin(void) { return mRegistryList.begin(); } The errors are: no 'typename std::vector<registeredObject, std::allocator<_CharT> >::iterator FxRegistry<registeredObject>::begin()' member function declared in class 'FxRegistry<registeredObject>' template definition of non-template 'typename std::vector<registeredObject, std::allocator<_CharT> >::iterator FxRegistry<registeredObject>::begin()' How do I decide how to solve these and where do I start looking?

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  • C++ String tokenisation from 3D .obj files

    - by Ben
    I'm pretty new to C++ and was looking for a good way to pull the data out of this line. A sample line that I might need to tokenise is f 11/65/11 16/70/16 17/69/17 I have a tokenisation method that splits strings into a vector as delimited by a string which may be useful static void Tokenise(const string& str, vector<string>& tokens, const string& delimiters = " ") The only way I can think of doing it is to tokenise with " " as a delimiter, remove the first item from the resulting vector, then tokenise each part by itself. Is there a good way to do this all in one?

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  • What to return as an iterator when there is no container?

    - by DaClown
    I have an inheritance structure of objects with begin() and end() as pure virtual member functions in the base class. From this objects I'm planning to build a composite structure. This inner objects have std::vector member the begin() and end() get their data from. But in a leaf class there is no vector. Now I try to find a return value for begin() and end() in the leaf classes. What would be a good way to do that? The easiest way would be to have a vector member in the leaf classes with no elements in it to fuel begin() and end(), but this just doesn't feel right.

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  • Matlab - Propagate unit vectors on to the edge of shape boundaries

    - by Graham
    Hi I have a set of unit vectors which I want to propagate on to the edge of shape boundary defined by a binary image. The shape boundary is defined by a 1px wide white edge. I also have the coordinates of these points stored in a 2 row by n column matrix. The shape forms a concave boundary with no holes within itself made of around 2500 points. What would be the best method to do this? Are there some sort of ray tracing algorithms that could be used? Or would it be a case of taking the unit vector and multiplying it by a scalar and testing after multiplication if the end point of the vector is outside the shape boundary. When the end point of the unit vector is outside the shape, just find the point of intersection? Thank you very much in advance for any help!

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  • What's the bug in the following code ?

    - by Johannes
    #include <iostream> #include <algorithm> #include <vector> #include <boost/array.hpp> #include <boost/bind.hpp> int main() { boost::array<int, 4> a = {45, 11, 67, 23}; std::vector<int> v(a.begin(), a.end()); std::vector<int> v2; std::transform(v.begin(), v.end(), v2.begin(), boost::bind(std::multiplies<int>(), _1, 2)); std::copy(v2.begin(), v2.end(), std::ostream_iterator<int>(std::cout, " ")); } When run, this gives a creepy segmentation fault. Please tell me where I'm going wrong.

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  • Getting object coordinates from camera

    - by user566757
    I've implemented a camera in Java using a position vector and three direction vectors so I can use gluLookAt(); moving around in `ghost mode' works fine enough, but I want to add collision detection. I can't seem to figure out how to transform my position vector to coordinates in which OpenGL draws my objects. A rough sketch of my drawing loop is this: glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glLoadIdentity(); camera.setView(); drawer.drawTheScene(); I'm at a loss of how to proceed; looking at the ModelView matrix between calls and my position vector, I haven't found any kind of correlation.

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  • C++ Multithreaded server help

    - by kisplit
    Hello all, I'm working on a multithreaded server in c++ using boost-asio. Currently a design problem I'm running into deals with erasing a connection. I have a single server instance which holds a vector of connection objects. These connections receive commands which I parse. One command in particular deals with sending data to ALL connections in my vector. Now when a connection disconnects I'm currently erasing this connection from the vector and calling the destructor. It seems like I'm going to run into problems when someone 'SendAll' at the same time someone 'Disconnect'. Could anyone recommend a better design or just point me in the right direction? Any help greatly appreciated. Thanks

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  • Vectors for a 2D/3D World in Java

    - by jax
    I reading about Mathematics in Games and am wondering what is the best way to represent a Vector location in Java. I know there is a Vector class but I don't think this is what I need. There is also a Matrix class which looks like it may be what I want (a 1 dimensional matrix maybe). In particular, if I were to create a location Vector such as: v(x,y,z) where x,y and z are the coordinates in 3D space, what would be the best way to represent this in Java. It would be nice if I could also add, subtract and find the dot-product of Vectors. ideas?

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  • Sending message to multiple contacts of mobile by providing search facility in J2ME

    - by learn
    I wan to send the message to multiple contacts in the contactlist for(int j=0;j<vector.size();j++){ listofContacts=new ListofContacts(); listofContacts=(ListofContacts)vector.elementAt(j); list.setFitPolicy(1); list.append(listofContacts.contactname + " "+ listofContacts.contactno,null); System.out.println(listofContacts.contactname + " "+ listofContacts.contactno); } here i have taken all the contacts of contact list in vector and the listofcontacts is the class containing the name and number. To show the list of contacts for selection i am using list control with multiple choice. The code is working fine and message is sent to all the contacts which are selected by the user but as we know there may be 1000 of contacts in phonebook and in these case to select a particular user we have to scroll down the list. Now how to keep the search facility so that we can directly go to the required contact and if it is not possible with the list control which control is to be used so that multiple contacts can be selected and also search facility is available.

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