R Shiny is a fantastic framework to quickly develop and launch interactive data applications. I recently wrote some investing advice and was looking for a way to illustrate two case studies. Building on an RStudio template, I created a tool to visualize the return of an investment over time, allowing the user to modify each parameter and observe its effect:

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Find the full code here or below:

```
library(FinCal)
library(ggplot2)
library(tidyr)
library(shinythemes)
library(scales)
# Define UI for application that draws a histogram
ui <- shinyUI(fluidPage(theme = shinytheme("spacelab"),
# Application title
titlePanel("The Potential for Growth: Two Case Studies"),
p('An interactive tool to accompany the ', a(href = 'http://unboxed-analytics.com/life-hacking/fundamentals-of-investing/', '"Fundamentals of Investing"'), 'post.'),
# Sidebar with a slider input for number of bins
sidebarLayout(
sidebarPanel(
numericInput(
inputId = "rate",
label = "Yearly Rate of Return",
value = .06,
min = .01,
max = .15,
step = .01
),
p("Represented as a decimal."),
p(".06 = 6%"),
numericInput(
inputId = "years",
label = "Number of Years",
value = 43,
min = 3,
max = 50,
step = 1
),
numericInput(
inputId = "pv",
label = "Initial Outlay",
value = 2000,
min = 1000,
max = 100000,
step = 1000.
),
numericInput(
inputId = "pmt",
label = "Monthly Contribution",
value = 0,
min = 0,
max = 10000,
step = 100
),
numericInput(
inputId = "type",
label = "Payment Type",
value = 0,
min = 0,
max = 1,
step = 1
),
p("Indicates if payments occur at the end of each period (Payment Type = 0) or if payments occur at the beginning of each period (Payment Type = 1).")
),
mainPanel(plotOutput("finPlot"),
p("The grey line represents PRINCIPAL and the blue line represents PRINCIPAL + INTEREST."),
p("Case 1: Suppose you have $2,000 to invest. You use that money to purchase a low-cost, tax-efficient, diversified mutual fund offering an approximate yearly return of 6%."),
p("You purchase the mutual fund on your 22nd birthday and don’t check your account until your 65th birthday on the day of retirement. After 43 years, you would have over $26,200! Your money has doubled four times."),
p("Case 2: Suppose again you have $2,000 today to invest. You purchase shares of the same mutual and now, in addition to the initial investment, purchase $100 of additional shares each month. [Adjust the 'Monthly Contribution' sidebar parameter]"),
p("How much would you have at the end of 43 years? Over $268,400! You have passively created wealth through the market."))
)
))
# Define server logic required to draw a histogram
server <- shinyServer(function(input, output) {
output$finPlot <- renderPlot({
# processing
total <- fv(r = input$rate/12, n = 0:(12*input$years), pv = -input$pv, pmt = -input$pmt, type = input$type)
principal <- seq(input$pv, input$pv + (input$years*12)*(input$pmt+.000000001), input$pmt + .000000001)
interest <- total - principal
df <- data.frame(period = 0:(12*input$years), total, principal)
# plotting
ggplot(df, aes(x = period)) +
geom_line(aes(y = total), col = "blue", size = .85) +
geom_line(aes(y = principal), col = "black", size = .85) +
labs(x = "Period",
y = "") +
scale_y_continuous(labels = dollar) +
theme(legend.position="bottom") +
theme(legend.title = element_blank()) +
theme_minimal()
})
})
# Run the application
shinyApp(ui = ui, server = server)
```