# # = GSL::Function class # # == Class Methods # # — # * GSL::Function.alloc # # Constructor. #
# * ex: # require(“gsl”) # f = GSL::Function.alloc { |x| sin(x) } # # The value of the function is calculated by the method Function#eval, as # # p f.eval(x) # # The function can have parameters of arbitrary numbers. Here is an # example in case of exponential function f(x; a, b) = a*exp(-b*x). #
# f = GSL::Function.alloc { |x, params| # x: a scalar, params: an array # a = params; b = params # a*exp(-b*x) # } # To evaluate the function f(x) = 2*exp(-3*x), # f.set_params([2, 3]) # f.eval(x) # # == Methods # # — # * GSL::Function#eval(x) # * GSL::Function#call(x) # * GSL::Function#at(x) # * GSL::Function# # # These methods return a value of the function at x. # p f.eval(2.5) # p f.call(2.5) # p f # The argument x can be a scalar, a Vector, Matrix, Array or Range. # # — # * GSL::Function#set { |x| … } # * GSL::Function#set(proc, params) # # This method sets or resets the procedure of self, as # # f = GSL::Function.alloc { |x| sin(x) } # p f.eval(1.0) <- sin(1.0) # f.set { |x| cos(x) } # p f.eval(1.0) <- cos(1.0) # # — # * GSL::Function#set_params(params) # # This set the constant parameters of the function. # # == Graph # — # * GSL::Function#graph(x[, options]) # # This method uses GNU graph to plot the function self. # The argument x is given by a GSL::Vector or an Array. # # Ex: Plot sin(x) # f = Function.alloc { |x| Math::sin(x) } # x = Vector.linspace(0, 2*M_PI, 50) # f.graph(x, “-T X -g 3 -C -L ‘sin(x)’”) # # # == Example # A quadratic function, f(x) = x^2 + 2x + 3. # # >> require(“gsl”) # => true # >> f = Function.alloc { |x, param| x*x + param*x + param } # => #<GSL::Function:0x6e8eb0> # >> f.set_params(2, 3) # => #<GSL::Function:0x6e8eb0> # >> f.eval(2) <— Scalar # => 11 # >> f.eval(1..4) <— Range # => [6.0, 11.0, 18.0, 27.0] # >> f.eval([1, 2, 3]) <— Array # => [6.0, 11.0, 18.0] # >> f.eval(Matrix.alloc([1, 2], [3, 4])) <— GSL::Matrix # [ 6.000e+00 1.100e+01 # 1.800e+01 2.700e+01 ] # => #<GSL::Matrix:0x6dd1b4> # # back #