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lines 5-78 of file: example/user/trace_init.py
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# {xrst_begin user_trace_init.py}
# {xrst_spell
#     def
#     exp
# }
# {xrst_comment_ch #}
#
# Using Initialization Trace Option
# #################################
#
# Purpose
# *******
# This example shows how to use the
# :ref:`option_table@trace_init_fit_model` option.
#
# Integrands
# **********
# For this example there are one integrand, ``Sincidence`` .
#
# Nodes
# *****
# There three nodes.
# The first is called ``world`` and is the parent node for this example.
# The second (third) is called ``child_1`` (``child_2`` )
# and is a child of the parent node.
#
# True Iota
# *********
# For this example, the true model incidence rate *iota* is
# {xrst_code py}
def iota_true(age, node) :
    import math
    iota_parent  = 0.01 * (1 + age / 100.0)
    child_effect = 0.2
    if node == 'world' :
        return iota_parent
    if node == 'child_1' :
        return math.exp(+ child_effect) * iota_parent
    if node == 'child_2' :
        return math.exp(- child_effect) * iota_parent
    assert False
# {xrst_code}
#
# Model
# *****
#
# Parent Node
# ===========
# There is only one rate *iota* and it linear in age
# with knots at the age 0 and 100.
#
# Child Nodes
# ===========
# There is only one rate *iota* and it constant.
#
# Data
# ****
# There are six data points measuring Sincidence
# with the true value of *iota* .
# These correspond to ages 0 and 100 at each of the three nodes.
#
# trace_init_fit_model
# ********************
# The option :ref:`option_table@trace_init_fit_model`
# is set to true and the corresponding output is checked.
#
# Source Code
# ***********
# {xrst_literal
#     BEGIN PYTHON
#     END PYTHON
# }
#
# {xrst_end user_trace_init.py}