The analysis Folder
The contents of the analysis folder are below. The key is the line
that says, source('data-raw/fetch-raw-data.R'). This calls the
fetch-raw-data.R script so that when you run the code below, the raw
data are fetched and prepared (from scratch each time you run the
script). Then, the following contents of the analysis.R script test
the corn and soybean prices for the presence of unit roots via the ADF
test (Said and Dickey 1984).
# Filename: analysis.R
# This file performs statistical analysis. It could be just one file, so it doesn't neccessarly
# need it's own folder, but sometimes your analysis may get complicated enough that you want
# to compartmentalize it. Separating different types of analyses into different scripts contained
# in the same folder can facilitate this
library(urca)
library(vars)
# This line runs the source code that fetched your raw data and cleaned it. Now it is available
# for conducting analysis.
source('data-raw/fetch-raw-data.R')
# Store results of ADF tests for Corn and Soybeans in a list
adf <- list()
adf[[1]] <- ur.df(CZ2016, type = 'drift', lags = 5)
adf[[2]] <- ur.df(SX2016, type = 'drift', lags = 5)
# Store results of a Johansen cointegration test for Corn and Soybeans
jct <- ca.jo(cbind(CZ2016, SX2016), type = 'eigen', K = 5)
# Fit a VAR
lag_selection <- VARselect(cbind(CZ2016, SX2016), lag.max = 8)
var_model <- VAR(cbind(CZ2016, SX2016), p = 1, type = "const")
# Save these results so that it can be pulled into the manuscript without re-running analysis.
save(adf, jct, lag_selection, var_model, file = 'analysis-output/results.rda')
The analysis-output Folder
The last line of the code snippet above says,
save(adf, jct, lag_selection, var_model, file = 'analysis-output/results.rda').
What this does is save the objects that contain the adf, Johansen
cointegration, and VAR regression results to an .rda file called
results.rda in the analysis folder. This ‘R Data’ file can be read
in by R and the variable names, adf, jct, lag_selection, and
var_model are preserved when loaded later. We will load the
results.rda file into the tablesandfigures-example.Rmd document to
make tables and figures in the manuscript.