# Load packages

# Core
library(tidyverse)
library(tidyquant)

Goal

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

Choose your stocks.

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

1 Import stock prices

# Choose stocks

symbols <- c("NFLX", "AAPL", "VRTX")

# 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 = "quarterly",
                 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)

w_tbl <- tibble(symbols, w)

4 Build a portfolio

portfolio_returns_rebalanced_quarterly_tbl <- asset_returns_tbl %>%
    
    tq_portfolio(assets_col   = asset,
                 returns_col  = returns,
                 weights      = w_tbl,
                 col_rename   = "returns",
                 rebalance_on = "quarters")

portfolio_returns_rebalanced_quarterly_tbl
## # A tibble: 20 × 2
##    date       returns
##    <date>       <dbl>
##  1 2013-03-28  0.188 
##  2 2013-06-28  0.0766
##  3 2013-09-30  0.132 
##  4 2013-12-31  0.0817
##  5 2014-03-31 -0.0307
##  6 2014-06-30  0.164 
##  7 2014-09-30  0.0615
##  8 2014-12-31 -0.0344
##  9 2015-03-31  0.0792
## 10 2015-06-30  0.126 
## 11 2015-09-30 -0.0412
## 12 2015-12-31  0.0528
## 13 2016-03-31 -0.110 
## 14 2016-06-30 -0.0432
## 15 2016-09-30  0.0646
## 16 2016-12-30  0.0306
## 17 2017-03-31  0.178 
## 18 2017-06-30  0.0372
## 19 2017-09-29  0.0994
## 20 2017-12-29  0.0356
# write_rds(portfolio_returns_rebalanced_monthly_tbl,
#           "00_data/Ch03_portfolio_returns_rebalanced_monthly_tbl.rds")

5 Plot

portfolio_returns_rebalanced_quarterly_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 = "quarterly return")

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

portfolio_returns_rebalanced_quarterly_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 = "quarterly returns")