model_initialization {markets}

Model initialization

Description

Model initialization

Usage

## S4 method for signature 'diseq_basic'
initialize(
  .Object,
  quantity,
  price,
  demand,
  supply,
  subject,
  time,
  data,
  correlated_shocks = TRUE,
  verbose = 0
)

## S4 method for signature 'diseq_deterministic_adjustment'
initialize(
  .Object,
  quantity,
  price,
  demand,
  supply,
  subject,
  time,
  data,
  correlated_shocks = TRUE,
  verbose = 0
)

## S4 method for signature 'diseq_directional'
initialize(
  .Object,
  quantity,
  price,
  demand,
  supply,
  subject,
  time,
  data,
  correlated_shocks = TRUE,
  verbose = 0
)

## S4 method for signature 'diseq_stochastic_adjustment'
initialize(
  .Object,
  quantity,
  price,
  demand,
  supply,
  price_dynamics,
  subject,
  time,
  data,
  correlated_shocks = TRUE,
  verbose = 0
)

## S4 method for signature 'equilibrium_model'
initialize(
  .Object,
  quantity,
  price,
  demand,
  supply,
  subject,
  time,
  data,
  correlated_shocks = TRUE,
  verbose = 0
)

Arguments

.Object

The object to be Constructed.

quantity

The quantity variable of the system.

price

The price variable of the system.

demand

A formula representation of the right hand side of the demand equation.

supply

A formula representation of the right hand side of the supply equation.

subject

The subject identifier of the data set.

time

The time identifier of the data set.

data

The data set.

correlated_shocks

Should the model be estimated using correlated shocks?

verbose

Verbosity level.

price_dynamics

A formula representation of the price equation.

Details

The following two subsections describe the common initialization steps of all market model classes.

Variable construction

The constructor prepares the model's variables using the passed specifications. The specification variables are expected to be of type language. The right hand side specifications of the system are expected to follow the syntax of formula. The construction of the model's data uses the variables extracted by these specification. The demand variables are extracted by a formula that uses the quantity on the left hand side and the demand on the right hand side of the formula. The supply variables are constructed by the quantity and the supply inputs. In the case of the diseq_stochastic_adjustment model, the price dynamics' variables are extracted using the price dynamics input. The price dynamics for the diseq_stochastic_adjustment should contain only terms other than that of excess demand. The excess demand term of the price equation is automatically generated by the constructor.

Data preparation

1. If the passed data set contains rows with NA values, they are dropped. If the verbosity level allows warnings, a warning is emitted reporting how many rows were dropped.

2. After dropping the rows, factor levels may be invalidated. If needed, the constructor readjusts the factor variables by removing the unobserved levels. Factor indicators and interaction terms are automatically created.

3. The primary key column is constructed by pasting the values of the columns of the subject and time variables.

4. In the cases of the diseq_directional, diseq_deterministic_adjustment, and the diseq_stochastic_adjustment models, a column with lagged prices is constructed. Since lagged prices are unavailable for the observations of the first time point, these observations are dropped. If the verbosity level allows the emission of information messages, the constructor prints the number of dropped observations.

5. In the cases of the diseq_directional and the diseq_stochastic_adjustment models, a column with price differences is created.

Value

The initialized model.

Functions

• initialize(diseq_basic): Basic disequilibrium model base constructor

• initialize(diseq_deterministic_adjustment): Disequilibrium model with deterministic price adjustment constructor

• initialize(diseq_directional): Directional disequilibrium model base constructor

• initialize(diseq_stochastic_adjustment): Disequilibrium model with stochastic price adjustment constructor

• initialize(equilibrium_model): Equilibrium model constructor

Examples

simulated_data <- simulate_data(
  "diseq_basic", 500, 3, # model type, observed entities, observed time points
  -0.9, 8.9, c(0.3, -0.2), c(-0.03, -0.01), # demand coefficients
  0.9, 6.2, c(0.03), c(-0.05, 0.02) # supply coefficients
)

# initialize the model
model <- new(
  "diseq_basic", # model type
  subject = id, time = date, quantity = Q, price = P,
  demand = P + Xd1 + Xd2 + X1 + X2, supply = P + Xs1 + X1 + X2,
  simulated_data, # data
  correlated_shocks = FALSE # use independent shocks
)

show(model)
simulated_data <- simulate_data(
  # model type, observed entities and time points
  "diseq_deterministic_adjustment", 500, 3,
  # demand coefficients
  -0.9, 8.9, c(0.03, -0.02), c(-0.03, -0.01),
  # supply coefficients
  0.9, 4.2, c(0.03), c(0.05, 0.02),
  # price adjustment coefficient
  1.4
)

# initialize the model
model <- new(
  "diseq_deterministic_adjustment", # model type
  subject = id, time = date, quantity = Q, price = P,
  demand = P + Xd1 + Xd2 + X1 + X2, supply = P + Xs1 + X1 + X2,
  simulated_data, # data
  correlated_shocks = TRUE # allow shocks to be correlated
)

show(model)

simulated_data <- simulate_data(
  "diseq_directional", 500, 3, # model type, observed entities, observed time points
  -0.2, 4.3, c(0.03, 0.02), c(0.03, 0.01), # demand coefficients
  0.0, 4.0, c(0.03), c(0.05, 0.02) # supply coefficients
)

# in the directional model prices cannot be included in both demand and supply
model <- new(
  "diseq_directional", # model type
  subject = id, time = date, quantity = Q, price = P,
  demand = P + Xd1 + Xd2 + X1 + X2, supply = Xs1 + X1 + X2,
  simulated_data, # data
  correlated_shocks = TRUE # allow shocks to be correlated
)

show(model)

simulated_data <- simulate_data(
  # model type, observed entities and time points
  "diseq_stochastic_adjustment", 500, 3,
  # demand coefficients
  -0.1, 9.8, c(0.3, -0.2), c(0.6, 0.1),
  # supply coefficients
  0.1, 7.1, c(0.9), c(-0.5, 0.2),
  # price adjustment coefficient
  1.4, 3.1, c(0.8)
)

# initialize the model
model <- new(
  "diseq_stochastic_adjustment", # model type
  subject = id, time = date, quantity = Q, price = P,
  demand = P + Xd1 + Xd2 + X1 + X2, supply = P + Xs1 + X1 + X2,
  price_dynamics = Xp1,
  simulated_data, # data
  correlated_shocks = TRUE # allow shocks to be correlated
)

show(model)
simulated_data <- simulate_data(
  "equilibrium_model", 500, 3, # model type, observed entities and time points
  -0.9, 14.9, c(0.3, -0.2), c(-0.03, -0.01), # demand coefficients
  0.9, 3.2, c(0.3), c(0.5, 0.02) # supply coefficients
)

# initialize the model
model <- new(
  "equilibrium_model", # model type
  subject = id, time = date, quantity = Q, price = P,
  demand = P + Xd1 + Xd2 + X1 + X2, supply = P + Xs1 + X1 + X2,
  simulated_data, # data
  correlated_shocks = TRUE # allow shocks to be correlated
)

show(model)