I would like to display flow lines (OD-lines) using leaflet in Shiny and sofar I can successfully map all the lines I want. But I also want to change the line width so that each line will have a different linewidth depending on the attribute they have. I am trying to get the values for weight with the following code but it does not work:

  values <- reactive({

    anzhl <-isolate(values()[,10])

    leafletProxy("zones", data = values()) %>% 
    removeShape(layerId="liID") %>% 
    addPolylines(lng=~x_coor, lat=~y_coor, stroke=TRUE, layerId="liID", color="black", weight=sum(anzhl())/100)})

I get the following error message:

Warning: Error in observerFunc: could not find function "anzhl"
Stack trace (innermost first):
    56: observerFunc [E:\.../server.R#118]
     1: runApp
ERROR: [on_request_read] connection reset by peer

What am I doing wrong and is it ever possible to change the line widths with the values called within an interactive session.

1 Answer 1


Read the error:

 Warning: Error in observerFunc: could not find function "anzhl"

then look at where your code mentions anzhl:


You have () there, which makes R think it needs to call a function. anzhl is not a function, its a vector or some other data thing. If you want the sum of all the values just do sum(anzhl).

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