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tira/math/function.h 4.89 KB
ce6381d7   David Mayerich   updating to TIRA
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  #ifndef RTS_FUNCTION_H
  #define RTS_FUNCTION_H
  
  #include <string>
  
  namespace stim{
  
  //template class for a one-dimensional function
  template <class Tx, class Ty>
  class function
  {
  protected:
  
  	std::vector<Tx> X;
  	std::vector<Ty> Y;
  	Ty range[2];
  	Ty bounding[2];
  
  	//comparison function for searching lambda
  	static bool findCeiling(Tx ax, Tx bx){
  	    return (ax > bx);
  	}
  
  	//process a string to extract a function (generally delimited by tabs, commas, spaces, etc.)
  	void process_string(std::string s){
  		std::stringstream ss(s);
  
  		Tx x;
  		Ty y;
  		std::string line;
  
  		while(!ss.eof()){
  			
  			std::getline(ss, line);
  			if(line[0] == '#') continue;
  
  			std::stringstream lstream(line);
  
  			lstream>>x;			//read the x value
  			lstream>>y;			//read the y value
  
  			if(ss.eof()) break;
  			insert(x, y);			//insert the read value into the function
  		}	
  	}
  
  	void update_range(Ty y){
  		//if the function is empty, just set the range to the given value
  		if(X.size() == 0){
  			range[0] = range[1] = y;
  		}
  
  		//otherwise compare the values and set them appropriately
  		if(y < range[0]) range[0] = y;
  		if(y > range[1]) range[1] = y;
  	}
  
  
  public:
  	function(){
  		range[0] = range[1] = 0;
  		bounding[0] = bounding[1] = 0;
  	}
  
  	//linear interpolation
  	Ty linear(Tx x) const
  	{
  		if(X.size() == 0)	return bounding[0];	//return zero if the function is empty
  		//return bounding values if x is outside the sample domain
  		if(x < X[0]) return bounding[0];
  		if(x > X.back()) return bounding[1];
  
  		unsigned int N = X.size();			//number of sample points
  
  		//declare an iterator
  		typedef typename std::vector< Tx >::iterator f_iter;	//declare an iterator
  		f_iter it;
  
  		//find the first X-coordinate that is greater than x
  		unsigned int i;
  		for(i = 0; i<N; i++){
  			if(X[i] > x)
  				break;
  		}
  		//i currently holds the ceiling
  
  		//if the wavelength is past the end of the list, return the last sample point
  		if(i == N) return Y.back();
  		//if the wavelength is before the beginning of the list, return the front
  		else if(i == 0) return Y[0];
  		//otherwise interpolate
  		else{
  		    Tx xMax = X[i];
  		    Tx xMin = X[i-1];
  
  		    Tx a = (x - xMin) / (xMax - xMin);
  		    Ty riMin = Y[i - 1];
  		    Ty riMax = Y[i];
  		    Ty interp = riMax * a + riMin * (1 - a);
  		    return interp;
  		}
  	}
  
  	///add a data point to a function
  	void insert(Tx x, Ty y)
  	{
  		unsigned int N = X.size();		//number of sample points
  
  		update_range(y);			//update the range of the function
  
  		if(N == 0 || X[N-1] < x){
  			X.push_back(x);
  			Y.push_back(y);
  			return;
  		}
  
  		//declare an iterator and search for the x value
          typename std::vector< Tx >::iterator it;		
          it = search(X.begin(), X.end(), &x, &x + 1, &function<Tx, Ty>::findCeiling);
  
          //if the function value is past the end of the vector, add it to the back
          if(*it == N){
          	X.push_back(x);
          	Y.push_back(y);
          }
          //otherwise add the value at the iterator position
          else{
  			X.insert(it, x);
  			Y.insert(Y.begin() + *it, y);
  		}
  
  	}
  
  	Tx getX(unsigned int i) const{
  		return X[i];
  	}
  
  	Ty getY(unsigned int i) const{
  		return Y[i];
  	}
  
  	///get the number of data points in the function
  	unsigned int getN() const{
  		return X.size();
  	}
  
  	//look up an indexed component
  	Ty operator[](int i) const{
  		if(i <= X.size()){
  			std::cout<<"ERROR: accessing non-existing sample point in 'function'"<<std::endl;
  			exit(1);
  		}
  		return Y[i];
  	}
  
  	///linear interpolation
  	Tx operator()(Tx x) const{
  		return linear(x);
  	}
  
  	//add a constant to the function
  	function<Tx, Ty> operator+(Ty r) const{
  
  		function<Tx, Ty> result;
  
  		//if there are points in the function
  		if(X.size() > 0){
  			//add r to every point in f
  			for(unsigned int i=0; i<X.size(); i++){
  				result.X.push_back(X[i]);
  				result.Y.push_back(Y[i] + r);
  			}
  		}
  		else{
  			result = r;
  		}
  
  		return result;
  	}
  
  	function<Tx, Ty> & operator= (const Ty & rhs){		
  		X.clear();
  		Y.clear();
  		bounding[0] = bounding[1] = rhs;	//set the boundary values to rhs
  		if(rhs != 0)						//if the RHS is zero, just clear, otherwise add one value of RHS
  			insert(0, rhs);
  
  		return *this;
  	}
  
  
  	//output a string description of the function (used for console output and debugging)
  	std::string str(){
  		unsigned int N = X.size();
  
  		std::stringstream ss;
  		ss<<"# of samples: "<<N<<std::endl;
  
  		if(N == 0) return ss.str();
  
  		ss<<"domain: ["<<X[0]<<", "<<X[X.size()-1]<<"]"<<std::endl;
  		ss<<"range: ["<<range[0]<<", "<<range[1]<<"]"<<std::endl;
  
  
  		return ss.str();
  
  	}
  	std::string str_vals(){
  		std::stringstream ss;
  
  		unsigned int N = X.size();		//number of sample points
  		//output each function value
  		for(unsigned int i = 0; i<N; i++){
  			if(i != 0) ss<<std::endl;
  			ss<<X[i]<<", "<<Y[i];
  		}
  
  		return ss.str();
  
  	}
  
  	void load(std::string filename){
  		std::ifstream t(filename.c_str());
  		std::string str((std::istreambuf_iterator<char>(t)),
  		std::istreambuf_iterator<char>());
  
  		process_string(str);
  	}
  
  
  };
  
  }	//end namespace rts
  
  
  #endif