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0_structs_and_generic_reversals.jl
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0_structs_and_generic_reversals.jl
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import Base.+, Base.-, Base./, Base.*, Base.^
import Base.sort
import SchumakerSpline.evaluate
abstract type UnivariateFunction end
struct Undefined_Function <: UnivariateFunction
end
Base.broadcastable(e::Undefined_Function) = Ref(e)
struct PE_Function{F<:Real,I<:Integer} <: UnivariateFunction
# a exp(b(x-base)) (x-base)^d
a_::F
b_::F
base_::F
d_::I
function PE_Function(a_::R,b_::S,base_::T,d_::I) where R<:Real where S<:Real where T<:Real where I<:Integer
promo_type = promote_type(T,S,T)
if d_ < 0
error("Negative polynomial powers are not supported by this package")
# These are banned due to the complications for calculus. Most
# divisions are not allowed for the same reason.
elseif (abs(b_) < tol) & (d_ == 0)
return new{promo_type,I}(promo_type(a_),promo_type(0.0),promo_type(0.0),I(0))
elseif abs(a_) < tol
return new{promo_type,I}(promo_type(0.0),promo_type(0.0),promo_type(0.0),I(0))
else
return new{promo_type,I}(promo_type(a_),promo_type(b_),promo_type(base_),I(d_))
end
end
function PE_Function(a_::R,b_::S,base_::Union{Date,DateTime},d_::I) where R<:Real where S<:Real where I<:Real
new_base_ = years_from_global_base(base_)
return PE_Function(a_, b_, new_base_, d_)
end
function PE_Function{Q,N}(a_::R,b_::S,base_::T,d_::I) where Q<:Real where N<:Integer where R<:Real where S<:Real where T<:Real where I<:Integer
return new{Q,N}(Q(a_), Q(b_), Q(base_), N(d_))
end
end
Base.broadcastable(e::PE_Function) = Ref(e)
struct Sum_Of_Functions <: UnivariateFunction
functions_::Union{Array{PE_Function,1},Array{PE_Function{<:Real,<:Integer},1}}
function Sum_Of_Functions(funcs::Sum_Of_Functions)
return funcs
end
function Sum_Of_Functions(funcs::AbstractArray)
undefined_funcs = funcs[isa.(funcs, Ref(Undefined_Function))]
if length(undefined_funcs) > 0
return Undefined_Function()
end
functions_ = clean_array_of_functions(funcs)
return new(functions_)
end
end
Base.broadcastable(e::Sum_Of_Functions) = Ref(e)
struct Piecewise_Function <: UnivariateFunction
starts_::Array{<:Real,1}
functions_::Array{UnivariateFunction,1}
function Piecewise_Function(starts::Array{<:Real,1}, functions::Array)
if !issorted(starts)
error("Piecewise_Function must be constructed with a sorted increasing list of starts and the corresponding functions.")
end
if starts[1] != -Inf
starts = vcat(-Inf, starts)
functions = vcat(Undefined_Function(), functions)
end
len = length(starts)
if starts[len] == Inf
starts = starts[1:(len-1)]
functions = functions[1:(len-1)]
end
starts_without_pw_parts, functions_without_pw_parts = deal_with_piecewise_inputs(starts, functions)
new(starts_without_pw_parts, functions_without_pw_parts)
end
function Piecewise_Function(starts::Union{Array{DateTime,1},Array{Date,1},Array{Union{DateTime,Date},1}}, functions::Array)
starts_ = years_from_global_base.(starts)
return Piecewise_Function(starts_, functions)
end
function Piecewise_Function(start::Real, func)
return Piecewise_Function([start], [func])
end
function Piecewise_Function(start::Union{Date,DateTime}, func)
start_float = years_from_global_base(start)
return Piecewise_Function(start_float, func)
end
end
Base.broadcastable(e::Piecewise_Function) = Ref(e)
function sort(funcs::Array{PE_Function,1})
len = length(funcs)
attributes = hcat(map(f -> f.d_, funcs), map(f -> f.base_, funcs), map(f -> f.b_, funcs) )
ordering = convert(Array{Int}, sortslices(hcat(attributes, 1:len) , dims = 1)[:,4])
return funcs[ordering]
end
function trim_piecewise_function(func::Piecewise_Function, left_limit::Real, right_limit::Real)
if func.starts_[1] != -Inf
starts_ = [-Inf, left_limit, right_limit]
funcs_ = [Undefined_Function(), func, Undefined_Function()]
else
starts_ = [left_limit, right_limit]
funcs_ = [func, Undefined_Function()]
end
return Piecewise_Function(starts_, funcs_)
end
function deal_with_piecewise_inputs(starts::Array{<:Real,1}, functions::Array)
where_are_pw_bits = findall(typeof.(functions) .== UnivariateFunctions.Piecewise_Function)
if length(where_are_pw_bits) < 1
return starts, functions
else
first_pw_slice_i = where_are_pw_bits[1]
pw = functions[first_pw_slice_i]
from = starts[first_pw_slice_i]
if length(starts) > first_pw_slice_i
to = starts[first_pw_slice_i+1]
else
to = Inf
end
pw_starts, pw_funcs = take_piecewise_slice(pw.starts_, pw.functions_,from, to)
pw_starts[1] = from
new_starts = vcat(first_entries(starts, first_pw_slice_i-1), pw_starts, last_entries(starts, length(starts) - first_pw_slice_i))
new_funcs = vcat(first_entries(functions, first_pw_slice_i-1), pw_funcs, last_entries(functions, length(starts) - first_pw_slice_i))
return deal_with_piecewise_inputs(new_starts, new_funcs)
end
end
function first_entries(vec::Array, how_many::Integer)
if how_many < 1
return Array{Any,1}()
elseif how_many > length(vec)
return vec
else
return vec[1:how_many]
end
end
function last_entries(vec::Array, how_many::Integer)
if how_many < 1
return Array{Any,1}()
elseif how_many > length(vec)
return vec
else
leng = length(vec)
return vec[(leng-how_many+1):leng]
end
end
function take_piecewise_slice(starts::Array{<:Real,1}, functions::Array, from::Real, to::Real)
from_i = searchsortedlast(starts, from)
to_i = searchsortedlast(starts, to)
return starts[from_i:to_i], functions[from_i:to_i]
end
function find(a::BitArray)
len = length(a)
indices = Array{Int,1}()
for i in 1:len
if a[i]
append!(indices, i)
end
end
return indices
end
function rationalise_array_of_functions(funcs::Array{PE_Function,1})
len = length(funcs)
if len < 2
return funcs
end
attributes = hcat(map(f -> f.b_, funcs), map(f -> f.base_, funcs), map(f -> f.d_, funcs) )
multipliers = map(f -> f.a_, funcs)
unique_attributes = unique(attributes, dims = 1)
new_len = size(unique_attributes)[1]
new_funcs = Array{PE_Function,1}(undef,new_len)
for i in 1:new_len
atts = transpose(unique_attributes[i,:])
which_multipliers = all(attributes .== atts, dims=2)
multiplier = sum(multipliers[find(which_multipliers)])
new_funcs[i] = PE_Function(multiplier, atts[1], atts[2], convert(Int, atts[3]))
end
return new_funcs
end
function clean_array_of_functions(funcs::Array)
undefined_funcs = funcs[isa.(funcs, Ref(Undefined_Function))]
piecewise_funcs = funcs[isa.(funcs, Ref(Piecewise_Function))]
if length(undefined_funcs) > 0
return Undefined_Function()
elseif length(piecewise_funcs) > 0
error("You cannot directly construct a Sum_Of_Functions with a Piecewise_Function in the input array. Instead add up the piecewise functions directly, for instance typing 'f1 + f2' for the two piecewise functions.")
end
pe_funcs = funcs[isa.(funcs, Ref(PE_Function))]
pe_funcs = pe_funcs[abs.(map( x -> x.a_, pe_funcs)) .>= eps()]
sum_funcs = funcs[isa.(funcs, Ref(Sum_Of_Functions))]
if length(sum_funcs) > 0
for sf in sum_funcs
pe_funcs_in_sf = clean_array_of_functions(sf.functions_)
pe_funcs = vcat(pe_funcs, pe_funcs_in_sf)
end
end
if length(pe_funcs) == 0
return [PE_Function(0.0,0.0,0.0,0)]
end
simplified_functions = rationalise_array_of_functions(convert(Array{PE_Function,1}, pe_funcs))
return simplified_functions
end
function +(number::Real, f::UnivariateFunction)
return +(f,number)
end
function -(number::Real, f::UnivariateFunction)
return +(number, -1*f)
end
function *(number::Real, f::UnivariateFunction)
return *(f,number)
end
function /(number::Real, f::UnivariateFunction)
error("It is not possible yet to divide scalars by UnivariateFunctions")
end
function ^(number::Real, f::UnivariateFunction)
error("It is not possible yet to raise to the power of a UnivariateFunctions")
end
function evaluate(f::UnivariateFunction, d::Union{Date,DateTime})
date_in_relation_to_global_base = years_from_global_base(d)
return evaluate(f, date_in_relation_to_global_base)
end
function evaluate(f::UnivariateFunction, x::DatePeriod)
return evaluate(f, period_length(x))
end
function ^(f1::UnivariateFunction,num::Integer) # This will get overridden for undefined and zeros.
if num < 0
error("Cannot raise any univariate function to a negative power")
elseif num == 0
return PE_Function(1.0,0.0,0.0,0)
elseif num == 1
return f1
elseif num == 2
return f1 * f1
else
product = f1 * f1
for i in 1:(num-2)
product = product * f1
end
return product
end
end
function change_base_of_PE_Function(f::PE_Function, new_base::Real)
old_base = f.base_
diff = new_base - old_base
if abs(diff) < tol
return f
end
# First the exponential part.
new_a = f.a_ * exp(f.b_*diff)
if new_a < tol
error("Underflow problem. Changing to this base cannot be done")
end
# Now the polynomial part.
if f.d_ == 0
return PE_Function(new_a, f.b_, new_base, 0)
else
n = f.d_
funcs = Array{UnivariateFunction,1}(undef,n+1)
for r in 0:n
binom_coeff = factorial(n) / (factorial(r) * factorial(n-r))
new_multiplier = binom_coeff * new_a * diff^r
new_func = PE_Function(new_multiplier, f.b_, new_base, n-r )
funcs[r+1] = new_func
end
return Sum_Of_Functions(funcs)
end
end
# Conversions for linearly rescaling inputs.
function convert_to_linearly_rescale_inputs(f::Undefined_Function, alpha::Real, beta::Real)
return f
end
function convert_to_linearly_rescale_inputs(f::PE_Function, alpha::Real, beta::Real)
# We want the change the function so that whenever we put in x it is like we put in alpha x + beta.
beta = beta / alpha
alpha = 1.0/alpha
new_base_ = (f.base_ + beta)/alpha
new_multiplier = f.a_ * alpha^(f.d_)
new_power_ = f.b_ * alpha
return PE_Function(new_multiplier, new_power_, new_base_, f.d_)
end
function convert_to_linearly_rescale_inputs(f::Sum_Of_Functions, alpha::Real, beta::Real)
funcs = convert_to_linearly_rescale_inputs.(f.functions_, alpha,beta)
return Sum_Of_Functions(funcs)
end
function convert_to_linearly_rescale_inputs(f::Piecewise_Function, alpha::Real, beta::Real)
new_starts_ = (f.starts_ .* alpha) .+ beta
funcs_ = convert_to_linearly_rescale_inputs.(f.functions_, alpha,beta)
return Piecewise_Function(new_starts_, funcs_)
end