Troubleshooting

Common Errors and Fixes

Layer type errors

Error: addIoLayer(): Unknown layer type 'scatter'. Did you mean 'point'?

You used a type name that doesn’t exist. myIO suggests the closest match. Use one of the 20 supported types listed in ?addIoLayer.

# Wrong
addIoLayer(type = "scatter", ...)

# Right
addIoLayer(type = "point", ...)

Column not found

Error: addIoLayer(): Column 'weight' not found in data. Available columns: mpg, cyl, disp, hp, ...

The column name in your mapping doesn’t match any column in data. Check spelling and case — R column names are case-sensitive.

# Wrong — 'weight' doesn't exist in mtcars
addIoLayer(mapping = list(x_var = "weight", y_var = "mpg"), ...)

# Right — the column is 'wt'
addIoLayer(mapping = list(x_var = "wt", y_var = "mpg"), ...)

# Check your column names first
names(mtcars)

Invalid transform for type

Error: addIoLayer(): Transform 'lm' is not valid for layer type 'bar'.

Not all transforms work with all chart types. For example, lm only works with line (it produces fitted values for a trend line).

# Wrong — can't apply regression to a bar chart
addIoLayer(type = "bar", transform = "lm", ...)

# Right — use 'line' for trend lines
addIoLayer(type = "line", transform = "lm", ...)

Duplicate layer label

Error: addIoLayer(): Layer label 'data' already exists. Each layer must have a unique label.

Every layer needs a unique label. If you’re adding multiple layers, give each one a distinct name.

# Wrong — same label used twice
myIO() |>
  addIoLayer(type = "point", label = "data", ...) |>
  addIoLayer(type = "line", label = "data", ...)

# Right — unique labels
myIO() |>
  addIoLayer(type = "point", label = "scatter", ...) |>
  addIoLayer(type = "line", label = "trend", ...)

Argument type errors

Error: setSlider(): \param` must be a single character string, not numeric (123).`

The function tells you exactly what it expected and what you gave it. Check the argument types in ?setSlider.

# Wrong — param should be a string, not a number
setSlider(123, "label", 0, 1, 0.5)

# Right
setSlider("ci_level", "Confidence Level", 0.80, 0.99, 0.95)

Missing SharedData

Error: setLinked(): \shared_data` must be a SharedData object, not data.frame.`

setLinked() requires a crosstalk::SharedData object, not a raw data frame. Wrap your data first.

library(crosstalk)

# Wrong — passing raw data.frame
myIO() |> setLinked(mtcars)

# Right — wrap in SharedData
shared <- SharedData$new(mtcars, key = ~rownames(mtcars))
myIO() |>
  addIoLayer(type = "point", label = "pts",
    data = shared$data(), mapping = list(x_var = "wt", y_var = "mpg")) |>
  setLinked(shared)

Widget type errors

Error: Expected a myIO widget, got 'list'.

You passed something other than a myIO() widget to a setter function. Make sure the first argument in your pipe is myIO().

# Wrong — list is not a myIO widget
setBrush(list())

# Right — start with myIO()
myIO() |>
  addIoLayer(type = "point", label = "pts",
    data = mtcars, mapping = list(x_var = "wt", y_var = "mpg")) |>
  setBrush()

Chart Renders with Missing Layers

If your chart appears but is missing layers you expected, a JavaScript validation may have removed them. These errors are not visible in R by default.

How to diagnose

1. Run myIO_last_error() for guidance on where to find the error
2. Open the browser’s developer console (F12 in most browsers)
3. Look for warnings prefixed with [myIO]:
   • [myIO] Layer 'trend' removed: field 'y_var' must be numeric.
   • [myIO] Composition error: Cannot mix standalone chart types with other layers.

In Shiny

Read the error reactive input:

observeEvent(input$`myIO-chart-error`, {
  showNotification(input$`myIO-chart-error`, type = "error")
})

Shiny Input Reference

All myIO Shiny inputs follow myIO-{outputId}-{event}:

Input key	When it fires
myIO-{id}-error	JS validation or render error
myIO-{id}-rollover	Hover on data element
myIO-{id}-dragEnd	Point drag completed
myIO-{id}-brushed	Brush selection end/clear
myIO-{id}-annotated	Annotation add/remove/clear
myIO-{id}-slider-{param}	Slider value change