Title: GSL::Function class

1 Class Methods

GSL::Function.new
GSL::Function.alloc

Constructor for an instance of the Function class.

The value of the function is evaluated by the method eval, as

p f.eval(x)

The function can have constant parameters of arbitrary numbers. Here is an example in case of exponential function f(x; a, b) = a*exp(-b*x).

f = Function.new { |x, params|    # x: a scalar, params: an array
  a = params[0]
  b = params[1]
  a*exp(-b*x)
}

To evaluate the function f(x) = 2*exp(-3*x),

f.set_params([2, 3])
f.eval(x)

2 Methods

GSL::Function#eval(x)
GSL::Function#call(x)
GSL::Function#at(x)
GSL::Function#[x]

These methods return a value of the function at x.

p f.eval(2.5)
p f.call(2.5)
p f[2.5]
GSL::Function#set { |x| ... }
GSL::Function#set(proc, params)

This method sets or resets the procedure of self, as

f = GSL::Function.new { |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.

3 Example

A quadratic function, f(x) = x^2 + 2x + 3.

irb(main):001:0> require("gsl")
=> true
irb(main):002:0> f = Function.new { |x, param| x*x + param[0]*x + param[1] } 
=> #<GSL::Function:0x6e8eb0>
irb(main):003:0> f.set_params(2, 3)
=> #<GSL::Function:0x6e8eb0>
irb(main):004:0> f.eval(2)                             <--- Scalar
=> 11
irb(main):005:0> f.eval(1..4)                          <--- Range
=> [6.0, 11.0, 18.0, 27.0]
irb(main):006:0> f.eval([1, 2, 3])                     <--- Array
=> [6.0, 11.0, 18.0]
irb(main):007:0> f.eval(Matrix.new([1, 2], [3, 4]))    <--- GSL::Matrix
[ 6.000e+00 1.100e+01 
  1.800e+01 2.700e+01 ]
=> #<GSL::Matrix:0x6dd1b4>

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