Interactive Visualizations

This is the 4th chapter of the Dash Tutorial.
The previous chapter covered basic callback usage. The next chapter describes how to share data between callbacks. Just getting started? Make sure to install the necessary dependencies.

The dashCoreComponents package includes a Graph component called dccGraph.

dccGraph renders interactive data visualizations using the open source plotly.js JavaScript graphing library. Plotly.js supports over 35 chart types and renders charts in both vector-quality SVG and high-performance WebGL.

The figure argument in the dccGraph component is the same figure argument that is used by plotly. Check out the plotly.py documentation and gallery to learn more.

As we already saw, Dash components are described by a set of attributes.
Any of these attributes can be updated by callback functions, but only
a subset of these attributes are updated through user interaction, such as
typing inside a dccInput component or clicking an option
in a dccDropdown component.

The dccGraph component has four attributes that can change
through user-interaction: hoverData, clickData, selectedData,
relayoutData. These properties update when you hover over points, click on points, or
select regions of points in a graph.

For optimal user interaction and chart loading performance, Dash applications
in production should consider the Job Queue,
HPC, Datashader,
and horizontal scaling capabilities of
Dash Enterprise.

Here’s an simple example that prints these attributes to the screen.

library(dash)

app <- dash_app()
app %>% add_stylesheet('https://codepen.io/chriddyp/pen/bWLwgP.css')

pre_style <- list(
  border = 'thin lightgrey solid',
  overflowX = 'scroll'
)

figure_data <- list(
  list(
    x = c(1, 2),
    y = c(1, 2),
    name = 'apple',
    mode = 'markers',
    marker = list(size = 20)
  ),
  list(
    x = c(1, 2),
    y = c(3, 4),
    name = 'orange',
    mode = 'markers',
    marker = list(size = 20)
  )
)

app %>% set_layout(
  dccGraph(
    id = 'basic-interactions',
    figure = list(
      data = figure_data,
      layout = list(
        clickmode = 'event+select'
      )
    )
  ),

  div(
    className = 'row',

    div(
      dccMarkdown(
        "
          **Hover Data**
          Mouse over values in the graph.
          "
      ),
      html$pre(id = 'hover-data', style = pre_style),
      className = 'three columns'
    ),

    div(
      dccMarkdown(
        "
          **Click Data**
          Click on points in the graph.
          "
      ),
      html$pre(id = 'click-data', style = pre_style),
      className = 'three columns'
    ),

    div(
      dccMarkdown(
        "
          **Selection Data**
          Choose the lasso or rectangle tool in the graph's menu
          bar and then select points in the graph.
          Selection data also accumulates (or un-accumulates) selected
          data if you hold down the shift button while clicking.
          "
      ),
      html$pre(id = 'selected-data', style = pre_style),
      className = 'three columns'
    ),

    div(
      dccMarkdown(
        "
          **Zoom and Relayout Data**
          Click and drag on the graph to zoom or click on the zoom
          buttons in the graph's menu bar.
          Clicking on legend items will also fire
          this event.
          "
      ),
      html$pre(id = 'relayout-data', style = pre_style),
      className = 'three columns'
    )
  )
)

json_return <- function(data) {
  jsonlite::prettify(jsonlite::toJSON(data), indent = 2)
}

app %>% add_callback(
  output('hover-data', 'children'),
  input('basic-interactions', 'hoverData'),
  function(hoverData) {
    json_return(hoverData)
  }
)

app %>% add_callback(
  output('click-data', 'children'),
  input('basic-interactions', 'clickData'),
  function(clickData) {
    json_return(clickData)
  }
)

app %>% add_callback(
  output('selected-data', 'children'),
  input('basic-interactions', 'selectedData'),
  function(selectedData) {
    json_return(selectedData)
  }
)

app %>% add_callback(
  output('relayout-data', 'children'),
  input('basic-interactions', 'relayoutData'),
  function(relayoutData) {
    json_return(relayoutData)
  }
)

app %>% run_app()

Hover Data

Mouse over values in the graph.


Click Data

Click on points in the graph.


Selection Data

Choose the lasso or rectangle tool in the graph’s menu
bar and then select points in the graph.

Note that if layout.clickmode = 'event+select', selection data also
accumulates (or un-accumulates) selected data if you hold down the shift
button while clicking.


Zoom and Relayout Data

Click and drag on the graph to zoom or click on the zoom
buttons in the graph’s menu bar.
Clicking on legend items will also fire
this event.



Update Graphs on Hover

Let’s update our world indicators example from the previous chapter by updating the time series when we hover over points in our scatter plot.

library(dash)

df <- read.csv('https://plotly.github.io/datasets/country_indicators.csv', header = TRUE, sep = ",")
available_indicators <- unique(df$Indicator.Name)
option_indicator <- lapply(available_indicators, function(x) list(label = x, value = x))

app <- dash_app()
app %>% add_stylesheet('https://codepen.io/chriddyp/pen/bWLwgP.css')

app %>% set_layout(
  div(
    style = list(
      borderBottom = 'thin lightgrey solid',
      backgroundColor = 'rgb(250, 250, 250)',
      padding = '10px 5px'
    ),

    div(
      dccDropdown(
        id = 'crossfilter-xaxis-column',
        options = option_indicator,
        value = 'Fertility rate, total (births per woman)'
      ),
      dccRadioItems(
        id = 'crossfilter-xaxis-type',
        options = list(list(label = 'Linear', value = 'linear'),
                       list(label = 'Log', value = 'log')),
        value = 'linear',
        labelStyle = list(display = 'inline-block')
      ),
      style = list(width = '49%', display = 'inline-block')
    ),

    div(
      dccDropdown(
        id = 'crossfilter-yaxis-column',
        options = option_indicator,
        value = 'Life expectancy at birth, total (years)'
      ),
      dccRadioItems(
        id = 'crossfilter-yaxis-type',
        options = list(list(label = 'Linear', value = 'linear'),
                       list(label = 'Log', value = 'log')),
        value = 'linear',
        labelStyle = list(display = 'inline-block')
      ),
      style = list(width = '49%', flaot = 'display', display = 'inline-block')
    ),

    div(
      dccGraph(
        id = 'crossfilter-indicator-scatter',
        hoverData = list(points = list(list(customdata = 'Japan')))
      ),
      style = list(
        width ='49%',
        display = 'inline-block',
        padding = '0 20'
      )
    ),

    div(
      dccGraph(id='x-time-series'),
      dccGraph(id='y-time-series'),
      style = list(display = 'inline-block', width = '49%')
    ),

    div(
      dccSlider(
        id = 'crossfilter-year--slider',
        min = 0,
        max = length(unique(df$Year))-1,
        marks = unique(df$Year),
        value = length(unique(df$Year))-1
      ),
      style = list(width = '49%', padding = '0px 20px 20px 20px')
    )
  )
)

app %>% add_callback(
  output('crossfilter-indicator-scatter', 'figure'),
  list(
    input('crossfilter-xaxis-column', 'value'),
    input('crossfilter-yaxis-column', 'value'),
    input('crossfilter-xaxis-type', 'value'),
    input('crossfilter-yaxis-type', 'value'),
    input('crossfilter-year--slider', 'value')
  ),
  function(xaxis_column_name, yaxis_column_name, xaxis_type, yaxis_type, year_value) {
    selected_year <- unique(df$Year)[year_value]
    traces <- list()

    if (selected_year %in% unique(df$Year)) {
      filtered_df <- df[df[["Year"]] %in% selected_year, ]
      traces[[1]] <- list(
        x = filtered_df[filtered_df$Indicator.Name %in% xaxis_column_name, "Value"],
        y = filtered_df[filtered_df$Indicator.Name %in% yaxis_column_name, "Value"],
        opacity=0.7,
        text = filtered_df[filtered_df$Indicator.Name %in% yaxis_column_name, "Country.Name"],
        customdata = filtered_df[filtered_df$Indicator.Name %in% yaxis_column_name, "Country.Name"],
        mode = 'markers',
        marker = list(
          'size'= 15,
          'opacity' = 0.5,
          'line' = list('width' = 0.5, 'color' = 'white')
        )
      )

      list(
        'data' = traces,
        'layout'= list(
          xaxis = list('title' = xaxis_column_name, 'type' = xaxis_type),
          yaxis = list('title' = yaxis_column_name, 'type' = yaxis_type),
          margin = list('l' = 40, 'b' = 30, 't' = 10, 'r' = 0),
          height = 450,
          hovermode = 'closest'
        )
      )
    }
  }
)

create_time_series <- function(dff, axis_type, title) {
  list(
    'data' = list(list(
      x = dff[['Year']],
      y = dff[['Value']],
      mode = 'lines+markers'
    )),
    'layout' = list(
      height = 225,
      margin = list('l' = 20, 'b' = 30, 'r' = 10, 't' = 10),
      'annotations' = list(list(
        x = 0, 'y' = 0.85, xanchor = 'left', yanchor = 'bottom',
        xref = 'paper', yref = 'paper', showarrow = FALSE,
        align = 'left', bgcolor = 'rgba(255, 255, 255, 0.5)',
        text = title[1]
      )),
      yaxis = list(type = axis_type),
      xaxis = list(showgrid = FALSE)
    )
  )
}

app %>% add_callback(
  output('x-time-series', 'figure'),
  list(
    input('crossfilter-indicator-scatter', 'hoverData'),
    input('crossfilter-xaxis-column', 'value'),
    input('crossfilter-xaxis-type', 'value')
  ),
  function(hoverData, xaxis_column_name, axis_type) {
    Country.Name <- hoverData$points[[1]]$customdata
    dff <- df[df[["Country.Name"]] %in% Country.Name, ]
    dff <- dff[dff[["Indicator.Name"]] %in% xaxis_column_name, ]
    title <- paste(c(Country.Name, xaxis_column_name), sep = '&lt;br&gt;')
    create_time_series(dff, axis_type, title)
  }
)

app %>% add_callback(
  output('y-time-series', 'figure'),
  list(
    input('crossfilter-indicator-scatter', 'hoverData'),
    input('crossfilter-yaxis-column', 'value'),
    input('crossfilter-yaxis-type', 'value')
  ),
  function(hoverData, yaxis_column_name, axis_type) {
    dff <- df[df[["Country.Name"]] %in% hoverData$points[[1]]$customdata, ]
    dff <- dff[dff[["Indicator.Name"]] %in% yaxis_column_name, ]
    create_time_series(dff, axis_type, yaxis_column_name)
  }
)

app %>% run_app()

Try moving the mouse over the points in the scatter plot on the left. Notice how the line graphs on the right update based on the point that you are hovering over.


Generic Crossfilter Recipe

Here’s a slightly more generic example for crossfiltering across a six-column data set. Each scatter plot’s selection filters the underlying dataset.

library(dash)

app <- dash_app()
app %>% add_stylesheet('https://codepen.io/chriddyp/pen/bWLwgP.css')

df <- as.data.frame(matrix(rnorm(180, seq(0, 50, 10), 0.1), ncol=6, byrow = TRUE))
colnames(df) <- paste("Column", 1:6)

app %>% set_layout(
  div(
    div(
      dccGraph(
        id = 'graph1',
        config = list(displayModeBar = FALSE)
      ),
      className = 'four columns'
    ),
    div(
      dccGraph(
        id = 'graph2',
        config = list(displayModeBar = FALSE)
      ),
      className='four columns'
    ),
    div(
      dccGraph(
        id = 'graph3',
        config = list(displayModeBar = FALSE)
      ),
      className = 'four columns'
    ),
    className = 'row'
  )
)

callback <- function(g1, g2, g3, x, y){
  selectedDatas = na.omit(c(g1, g2, g3))
  selectedpoints = as.numeric(rownames(df))
  selected_index =  lapply(1:length(selectedDatas[['points']]),
                           function(i) {selectedDatas[['points']][[i]][['customdata']]
                           })
  if(length(selected_index) > 0){
    selectedpoints = intersect(selectedpoints, selected_index)
  }

  data = list(
    x = df[[x]],
    y = df[[y]],
    text = as.numeric(rownames(df)),
    textposition = 'top',
    selectedpoints = unlist(lapply(selectedpoints, function(x){x-1})),
    customdata = as.numeric(rownames(df)),
    type = 'scatter',
    mode = 'markers+text',
    marker = list(
      color = 'rgb(0, 116, 217, 0.7)',
      size = 12,
      line = list(
        color = 'rgb(0, 116, 217)',
        width = 0.5
      )
    ),
    textfont = list(
      color = 'rgb(30, 30, 30, 1)'
    ),
    unselected = list(
      marker =list(
        opacity = 0.3
      ),
      textfont = list(
        # make text transparent when not selected
        color = 'rgb(0, 0, 0, 0)'
      )
    )
  )
  layout = list(
    clickmode = 'event+select',
    margin = list('l' = 15, 'r' = 0, 'b' = 15, 't' = 5),
    dragmode = 'select',
    hovermode = 'closest',
    xaxis = list(range = list(min(df[x]),max(df[x]))),
    yaxis = list(range = list(min(df[y]),max(df[y]))),
    showlegend = FALSE
  )
  figure = list(
    data = list(data
    ),
    layout = layout
  )
  shape = list(
    type = 'rect',
    line = list(
      width = 1,
      dash = 'dot',
      color = 'darkgrey'
    )
  )
  if(is.null(selectedDatas[['range']]) == FALSE){
    figure[['layout']]['shapes'] = list(list(list(
      'x0' = unlist(selectedDatas[['range']][['x']][1]),
      'x1' = unlist(selectedDatas[['range']][['x']][2]),
      'y0' = unlist(selectedDatas[['range']][['y']][1]),
      'y1' = unlist(selectedDatas[['range']][['y']][2]),shape)))
  }
  else{
    figure[['layout']]['shapes'] = list(list(list(
      'type' = 'rect',
      'x0' = min(df[x], na.rm = TRUE),
      'x1' = max(df[x], na.rm = TRUE),
      'y0' = min(df[y], na.rm = TRUE),
      'y1' = max(df[y], na.rm = TRUE),shape)))
  }
  return(figure)
}

app %>% add_callback(
  output('graph1', 'figure'),
  list(
    input('graph1', 'selectedData'),
    input('graph2', 'selectedData'),
    input('graph3', 'selectedData')
  ),
  function(g1, g2, g3){
    callback(g1, g2, g3, 'Column 1', 'Column 2')
  }
)

app %>% add_callback(
  output('graph2', 'figure'),
  list(
    input('graph2', 'selectedData'),
    input('graph1', 'selectedData'),
    input('graph3', 'selectedData')
  ),
  function(g2, g1, g3){
    callback(g2, g1, g3, 'Column 3', 'Column 4')
  }
)

app %>% add_callback(
  output('graph3', 'figure'),
  list(
    input('graph3', 'selectedData'),
    input('graph1', 'selectedData'),
    input('graph2', 'selectedData')
  ),
  function(g3, g1, g2){
    callback(g3, g1, g2, 'Column 5', 'Column 6')
  }
)

app %>% run_app()

Dash Data Selection Example

On every selection, the three graph callbacks are fired with the latest
selected regions of each plot. A dataframe is filtered based on the selected points and the graphs are replotted with the selected points highlighted and the selected region drawn as a dashed rectangle.

As an aside, if you find yourself filtering and visualizing highly-dimensional datasets, you should consider checking out the parallel coordinates chart type.


Current Limitations

There are a few limitations in graph interactions right now.
- It is not currently possible to customize the style of the hover interactions or the select box. This issue is being worked on in https://github.com/plotly/plotly.js/issues/1847.


There’s a lot that you can do with these interactive plotting features. If you need help exploring your use case, open up a thread in the Dash Community Forum.


The next chapter of the Dash User Guide explains how to share data between callbacks.

Dash Tutorial Part 5. Sharing Data Between Callbacks