From c85485db5350d1089aa810fbd6f13492a3a2bf52 Mon Sep 17 00:00:00 2001
From: Carson Sievert <cpsievert1@gmail.com>
Date: Thu, 21 Feb 2019 15:55:35 -0600
Subject: [PATCH] initial stab at crossfiltering with dbplot & spark

---
 inst/examples/shiny/crossfilter_dbplot/app.R | 96 ++++++++++++++++++++
 1 file changed, 96 insertions(+)
 create mode 100644 inst/examples/shiny/crossfilter_dbplot/app.R

diff --git a/inst/examples/shiny/crossfilter_dbplot/app.R b/inst/examples/shiny/crossfilter_dbplot/app.R
new file mode 100644
index 0000000000..4350afe256
--- /dev/null
+++ b/inst/examples/shiny/crossfilter_dbplot/app.R
@@ -0,0 +1,96 @@
+library(shiny)
+library(plotly)
+library(dplyr)
+library(sparklyr)
+library(dbplot)
+sc <- spark_connect(master = "local", version = "2.1.0")
+spark_flights <- copy_to(sc, nycflights13::flights, "flights")
+
+# Collect numeric variables to be shown as histograms in the crossfilter
+d <- select(
+  spark_flights, 
+  arr_time, 
+  dep_time, 
+  arr_delay, 
+  dep_delay, 
+  air_time, 
+  distance
+)
+
+# Generate an output container per variable
+ui <- fluidPage(
+  lapply(colnames(d), function(nm) plotlyOutput(nm, height = 200, width = "49%", inline = TRUE))
+)
+
+server <- function(input, output, session) {
+  
+  # These reactive values track the set of active brushes 
+  # Each reactive value corresponds to a different variable 
+  brush_ranges <- reactiveValues()
+  
+  # Filter the dataset based on every active brush range except for one (var)
+  # TODO: instead of filtering the entire dataset, 
+  # consider filtering a pre-binned dataset based on pixel resolution
+  # (perhaps using dbplot::bin_plot)
+  d_filter <- function(d, var = "arr_time") {
+    for (nm in setdiff(names(d), var)) {
+      rng <- brush_ranges[[nm]]
+      if (is.null(rng)) next
+      d <- filter(d, between(d[[nm]], min(rng), max(rng)))
+    }
+    d
+  }
+  
+  # Implement same render logic for each variable
+  lapply(colnames(d), function(nm) {
+    
+    sym <- as.symbol(nm)
+    counts_full <- db_compute_bins(spark_flights, !!sym)
+    
+    output[[nm]] <- renderPlotly({
+      
+      plot_ly(source = nm) %>%
+        add_bars(x = counts_full[[nm]], y = ~counts_full$count) %>%
+        layout(
+          dragmode = "select", 
+          selectdirection = "h",
+          xaxis = list(
+            title = nm,
+            range = range(counts_full[[nm]], na.rm = TRUE)
+          ),
+          yaxis = list(title = "")
+        )
+    })
+    
+    observeEvent(event_data("plotly_brushing", source = nm), ignoreNULL = FALSE, {
+      
+      # inform the world about the new brush range
+      brush_ranges[[nm]] <- event_data("plotly_brushing", source = nm)$x
+      
+      if (all(sapply(brush_ranges, function(x) length(x) == 0))) return()
+      
+      # update the bar heights of every view (except for the one being brushed)
+      for (var in setdiff(names(d), nm)) {
+        # views respect every brush except for their own 
+        d_filtered <- d_filter(d, var)
+        
+        # bin the filtered data based on the global binning definition
+        sym <- as.symbol(nm)
+        counts_filter <- db_compute_bins(
+          d_filtered, !!sym,
+          binwidth = diff(counts_full[[nm]][1:2])
+        )
+        
+        print(counts_filter)
+        # finally, update the bar heights
+        plotlyProxy(var, session) %>%
+          plotlyProxyInvoke("restyle", "y", list(counts_filter$count), 0) 
+      }
+    })
+    
+  })
+  
+}
+
+shinyApp(ui, server)
+