In InteractiveComplexHeatmap, we mainly use the
combination of InteractiveComplexHeatmapOutput() and
makeInteractiveComplexHeatmap() to create the interactive
heatmap widget in the Shiny application. The interactive widgets
contains many tools for manipulating heatmaps. However, sometimes users
may want to build their own interactive heatmap widget, e.g. to define
their own logic to respond to the clicking or brushing event on
heatmaps, while not use the one provided by
InteractiveComplexHeatmap. What they only want is the
information of the heatmap cells that were selected from heatmaps.
InteractiveComplexHeatmap also provides low-level
functions that directly return the information of rows and columns that
were selected from heatmap. I demonstrate the usage in the next example
where ui and server are defined as
follows:
ui = fluidPage(
...,
plotOutput("heatmap", click = "heatmap_click")
)
server = function(input, output, session) {
ht_obj = reactiveVal(NULL)
ht_pos_obj = reactiveVal(NULL)
output$heatmap = renderPlot({
...
ht = draw(Heatmap(mat))
ht_pos = htPositionsOnDevice(ht)
ht_obj(ht)
ht_pos_obj(ht_pos)
})
observeEvent(input$heatmap_click, {
pos = getPositionFromClick(input$heatmap_click)
df = selectPosition(ht_obj(), pos, mark = FALSE,
ht_pos = ht_pos_obj(), verbose = FALSE)
# do something with `df`
...
})
}There are two points that need to be noted.
draw() and htPositionsOnDevice() should
always be executed together and be put inside renderPlot()
so that positions of all heatmap slices can be correctly
calculated.getPositionFromClick() to retrieve the position of
the click on heatmap, then the position can be sent to
selectPosition() to correspond to the original matrix.
Similarly, getPositionFromBrush() and
selectArea() work together to retrieve rows and columns of
the matrix that correspond to the area selected from heatmap.The variable df contains row indices and column indices
for the cells that were selected (check the help page of
selectPosition() and selectArea() to see the
format of df). With this information, it is possible to
implement the interactive heatmap widget from scratch.
htShinyExample(5.8) demonstrates an example where the
interactivity of the heatmap is only implemented with the functions from
shiny. In this example, the main heatmap visualizes a
2D density distribution, and brushing on heatmap triggers a new 2D
density estimation but only on the selected subset of data. The source
code that generates this example is also includes in this web
application.