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Automating my ETF Portfolio

ShinyRWeb AppsPortfolio Management

Automating My ETF Portfolio with Shiny

The Problem

Managing a diversified ETF portfolio requires regular:

Doing this manually is tedious and error-prone. So I built an app.

The Solution

A Shiny web application that connects to my brokerage API and generates optimal trades.

R: Shiny App Core Logic▼ 
library(shiny)
library(tidyverse)
library(httr)


Define target allocation


target_allocation <- tibble(
  ticker = c("VTI", "VXUS", "BND", "VNQ"),
  target = c(0.50, 0.25, 0.20, 0.05)
)


calculate_rebalance <- function(holdings, targets, cash_available = 0) {


Join current holdings with targets


  portfolio <- holdings %>%
    full_join(targets, by = "ticker") %>%
    mutate(
      current_value = replace_na(shares * price, 0),
      target_value = target * (sum(current_value) + cash_available),
      difference = target_value - current_value,
      shares_to_trade = floor(difference / price)
    )


  return(portfolio)
}


UI


ui <- fluidPage(
  titlePanel("ETF Portfolio Manager"),
  sidebarLayout(
    sidebarPanel(
      numericInput("cash", "New Cash to Deploy ($)", 0),
      actionButton("refresh", "Refresh Holdings"),
      actionButton("calculate", "Calculate Trades")
    ),
    mainPanel(
      tableOutput("holdings"),
      plotOutput("allocation_chart"),
      tableOutput("trades")
    )
  )
)

Features