R plotly_click for heatmap not always working (due to NA)

[mvarewyck]

I tried to create a heatmap with R plotly in which the user can select a specific point ("block"). However, when the heatmap was based on a data.frame() then the clicked point information is only recorded if the first point in that row is not missing (z is not NA). For heatmaps based on a matrix() I don't experience any problem.

In the reproducible example: E.g. try to select the point with x = b and y = 1.

library(shiny)
library(plotly)

ui <- fluidPage(
        
        fluidRow(column(6, h4("Heatmap based on data.frame()"),
                        plotlyOutput("plot1"),
                        h4("Selected point in heatmap"),
                        verbatimTextOutput("selected1")
                ), 
                column(6, 
                        h4("Heatmap based on matrix()"),
                        plotlyOutput("plot2"),
                        h4("Selected point in heatmap"),
                        verbatimTextOutput("selected2")
                )
        )
)

server <- function(input, output) {
    
    randomValues <- rnorm(9)
    
    # Heatmap based on data.frame(): not working correctly, try to select x = b; y = 1
    output$plot1 <- renderPlotly({
                
                set.seed(1)
                myData <- data.frame(x = rep(letters[1:3], times = 3), 
                        y = rep(as.character(1:3), each = 3), value = randomValues)
                myData$value[1] <- NA
                
                plot_ly(
                        x = ~x, y = ~y, z = ~value, data = myData,
                        type = "heatmap", source = "plot1"
                )
                
            })
    
    
    output$selected1 <- renderPrint(
            event_data("plotly_click", source = "plot1")
    )
    
    
    # Heatmap based on matrix()
    output$plot2 <- renderPlotly({
                
                m <- matrix(randomValues, nrow = 3, ncol = 3, byrow = TRUE)
                m[1,1] <- NA
                
                plot_ly(
                        x = c("a", "b", "c"), y = as.character(1:3),
                        z = m, type = "heatmap", source = "plot2"
                )
                
                
            })
    
    
    output$selected2 <- renderPrint(
            event_data("plotly_click", source = "plot2")
    )
}

shinyApp(ui = ui, server = server)

[cpsievert]

Thanks for the report. Looks like event_data() is generally broken when x/y/z are all vectors of the same length (notice how z isn't reported in the cells that "work"). Turns out the pointNumber emitted by plotly.js refers to a relevant cell of the heatmap (i.e., it emits the relevant row and column index), but plotly isn't currently accounting for that.