10  Custom shocks

10.1 Overview

ems_custom_shock() allows for heterogeneous shocks specified on a tuple-by-tuple basis, supplied as a data frame or CSV file through input. Values are denominated in percentage change. Only the tuples present in input are shocked.

ems_custom_shock(var, input)

Argument	Type	Description
var	Character	Variable name as it appears in the model file
input	Data frame or Character	Data frame or path to a CSV file containing set columns and a Value column (percentage changes)

10.2 Full variable custom shocks

Custom shocks can be carried out over the full variable, with every tuple receiving a specified shock value. Here is a demonstration of 4 custom shocks carried out on all variable tuples for a range of variable dimensions with the GTAP-INT model.

Elements for data frame construction

time_steps <- c(0, 1, 2, 3)
REG <- c("chn", "usa", "row")
ENDW_COMM <- c("labor", "capital", "natlres", "land")
TRAD_COMM <- c("svces", "food", "crops", "mnfcs", "livestock")
PROD_COMM <- c("svces", "food", "crops", "mnfcs", "livestock", "zcgds")
MARG_COMM <- "svces"
ALLTIME <- seq(0, length(time_steps) - 1)

2D data frame and shock

pop <- expand.grid(
  REGr = REG,
  ALLTIMEt = ALLTIME,
  stringsAsFactors = FALSE
)

pop <- pop[do.call(order, pop), ]
pop$Value <- runif(nrow(pop))

pop_shk <- ems_custom_shock(
  var = "pop",
  input = pop
)

3D data frame and shock

aoall <- expand.grid(
  PROD_COMMj = PROD_COMM,
  REGr = REG,
  ALLTIMEt = ALLTIME,
  stringsAsFactors = FALSE
)

aoall <- aoall[do.call(order, aoall), ]
aoall$Value <- runif(nrow(aoall))

aoall_shk <- ems_custom_shock(
  var = "aoall",
  input = aoall
)

4D data frame and shock

afeall <- expand.grid(
  ENDW_COMMi = ENDW_COMM,
  PROD_COMMj = PROD_COMM,
  REGr = REG,
  ALLTIMEt = ALLTIME,
  stringsAsFactors = FALSE
)

afeall <- afeall[do.call(order, afeall), ]
afeall$Value <- runif(nrow(afeall))

afeall_shk <- ems_custom_shock(
  var = "afeall",
  input = afeall
)

5D data frame and shock

atall <- expand.grid(
  MARG_COMMm = MARG_COMM,
  TRAD_COMMi = TRAD_COMM,
  REGr = REG,
  REGs = REG,
  ALLTIMEt = ALLTIME,
  stringsAsFactors = FALSE
)

atall <- atall[do.call(order, atall), ]
atall$Value <- runif(nrow(atall))

atall_shk <- ems_custom_shock(
  var = "atall",
  input = atall
)

Multiple custom shocks are combined in a list for ems_deploy():

cmf_path <- ems_deploy(
  .data = dat,
  model = model,
  shock = list(pop_shk, aoall_shk, afeall_shk, atall_shk)
)

10.3 CSV input

A path to a CSV file can be passed to input instead of a data frame. The CSV must follow the same structure: one column per set index using the model-specific naming convention and a Value column. Column order is inconsequential.

pop_csv <- tempfile(fileext = ".csv")
write.csv(pop, pop_csv, row.names = FALSE)

pop_shk <- ems_custom_shock(
  var = "pop",
  input = pop_csv
)

This applies equally to partial variable shocks — only the tuples present in the file are shocked.

10.4 Partial variable custom shocks

Custom shocks are only carried out on tuples included within the input data frame or CSV. Here we carry out a custom shock (heterogenous values) across part of the aoall variable. The non-shocked values will remain at 0 due to their exogenous status.

aoall_full <- expand.grid(
  ACTSa = ACTS,
  REGr = REG,
  ALLTIMEt = ALLTIME,
  stringsAsFactors = FALSE
)
aoall_full$Value <- 0
aoall_full <- aoall_full[do.call(order, aoall_full), ]
aoall <- aoall_full[
  !(aoall_full$ACTSa == "crops" & aoall_full$REGr == "usa") &
  aoall_full$ALLTIMEt != 3,
]
aoall$Value <- runif(nrow(aoall))
aoall_shk  <- ems_custom_shock(var = "aoall",  input = aoall)

10.5 Chronological year input

For intertemporal models, the time dimension can be specified using chronological years instead of integer time steps by using a Year column in place of ALLTIMEt. The year values must correspond to the reference year and steps defined in ems_data().

time_steps <- c(2017, 2018, 2019, 2020)

dat <- ems_data(
  dat_input  = dat_input,
  par_input  = par_input,
  set_input  = set_input,
  time_steps = time_steps,
  REG  = "big3",
  ACTS = "macro_sector",
  ENDW = "labor_agg"
)

Construct the input data frame with a Year column rather than ALLTIMEt:

REG <- c("chn", "usa", "row")

pop <- expand.grid(
  REGr = REG,
  Year = time_steps,
  stringsAsFactors = FALSE
)

pop <- pop[do.call(order, pop), ]
pop$Value <- runif(nrow(pop))

pop_shk <- ems_custom_shock(
  var = "pop",
  input = pop
)

ems_custom_shock() is called identically — the Year column is recognised automatically and mapped to the corresponding integer time step internally.