# Load packages
 
# Core
library(tidyverse)
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library(tidyquant)
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Goal

Collect individual returns into a portfolio by assigning a weight to each stock

five stocks: “SPY”, “EFA”, “IJS”, “EEM”, “AGG”

from 2012-12-31 to 2017-12-31

1 Import stock prices

# Choose stocks
 
symbols <- c("SPY", "EFA", "IJS", "EEM", "AGG")
 
# Using tq_get() ----
prices <- tq_get(x = symbols,
                 get = "stock.prices",
                 from = "2012-12-31",
                 to = "2017-12-31")

2 Convert prices to returns

asset_returns_tbl <- prices %>%
 
    # Calculate monthly returns
    group_by(symbol) %>%
    tq_transmute(select = adjusted,
                 mutate_fun = periodReturn,
                 period = "monthly",
                 type = "log") %>%
    slice(-1) %>%
    ungroup() %>%
 
    # remane
    set_names(c("asset", "date", "returns"))
 
# period_returns = c("yearly", "quarterly", "monthly", "weekly")

3 Assign a weight to each asset

symbols <- asset_returns_tbl %>% distinct(asset) %>% pull()
 
w <- c(0.25,
       0.25,
       0.20,
       0.20,
       0.10)
 
w_tbl <- tibble(symbols, w)

4 Build a portfolio

portfolio_returns_rebalanced_monthly_tbl <- asset_returns_tbl %>%
   
    tq_portfolio(assets_col   = asset,
                 returns_col  = returns,
                 weights      = w_tbl,
                 col_rename   = "returns",
                 rebalance_on = "months")
## Warning in check_weights(weights, assets_col, map, x): Sum of weights does not
## equal 1.
portfolio_returns_rebalanced_monthly_tbl
## # A tibble: 60 × 2
##    date        returns
##    <date>        <dbl>
##  1 2013-01-31  0.0204 
##  2 2013-02-28 -0.00239
##  3 2013-03-28  0.0121 
##  4 2013-04-30  0.0174 
##  5 2013-05-31 -0.0128 
##  6 2013-06-28 -0.0247 
##  7 2013-07-31  0.0321 
##  8 2013-08-30 -0.0224 
##  9 2013-09-30  0.0511 
## 10 2013-10-31  0.0301 
## # ℹ 50 more rows
# write_rds(portfolio_returns_rebalanced_monthly_tbl,
#           "00_data/Ch03_portfolio_returns_rebalanced_monthly_tbl.rds")

5 Visualize

portfolio_returns_rebalanced_monthly_tbl %>%
   
    ggplot(aes(x = date, y = returns)) +
    geom_point(color = "cornflower blue") +
   
    # Formatting
    scale_x_date(breaks = scales::breaks_pretty(n = 6)) +
   
    labs(title = "Portfolio Returns Scatter",
         y = "monthly return")

portfolio_returns_rebalanced_monthly_tbl %>%
   
    ggplot(aes(returns)) +
    geom_histogram(fill = "cornflower blue",
                   binwidth = 0.005) +
   
    labs(title = "Portfolio Returns Distribution",
         y = "count",
         x = "returns")

portfolio_returns_rebalanced_monthly_tbl %>%
   
    ggplot(aes(returns)) +
    geom_histogram(fill = "cornflower blue",
                   binwidth = 0.01) +
    geom_density(aes(returns)) +
   
    labs(title = "Portfolio Histogram and Density",
         y = "distribution",
         x = "monthly returns")