Have nticks be respected when tickmode='array'

Examples for how it should work (using R’s plotly package)

Works fine:

library(plotly)
p <- plot_ly(
    width = 800,
    height = 500
  ) %>% layout(
    title = "fixed-ratio axes",
    xaxis = list(
      nticks = 10,
      domain = c(0, 0.45)
    ) )
p

Does not yet work:

library(plotly)
p <- plot_ly(
    width = 800,
    height = 500
  ) %>% layout(
    title = "fixed-ratio axes",
    xaxis = list(
      nticks = 10,
      domain = c(0, 0.45),
	tickmode='array'
    ) )
p

This feature is specifically important for creating cluster-heatmaps that allow more refined control over the number of ticks (see here)

[Alanocallaghan]

I think the desired output in this instance is for the user to be able to manually specify tick values and labels, but also apply the “auto” tick generating method.

For example, here I am creating a heatmap with categorical labels and automatic ticks by specifying the x co-ordinates, and tick generation works nicely: https://codepen.io/alanoc/pen/yXPgEp

However, in some cases it is desirable to map categorical scales to numerical scales, in order to present them side-by-side with other plots (and, more importantly, aligned), while maintaining meaningful categorical ticks. For example, heatmaps are commonly presented with dendrograms aligned to rows and columns, in order to show relationships between samples (eg, https://i.stack.imgur.com/1qTWn.png). To accomplish this, I would commonly specify a numeric axis and tick values, but character tick text. In this case, label overplotting is very common: https://codepen.io/alanoc/pen/WOXRLE

Perhaps tickvals and ticktext are not the right parameters to be used in this instance, as they do imply the values actually used for ticks; however I do think it would be useful to have this level of control.

[etpinard]

Merged with https://github.com/plotly/plotly.js/issues/1946