selecting series in Shiny with p_replace

sel.serie.Rmd

---
title: "Select Serie"
output: 
  flexdashboard::flex_dashboard:
    orientation: columns
    vertical_layout: fill
runtime: shiny
---

```{r setup, include=FALSE}
#' replace chart series interactively in Shiny
#' idea from https://github.com/EKtheSage
#' RE: https://github.com/JohnCoene/echarts4r/issues/325
library(flexdashboard)
library(shiny)
library(dplyr)
library(echarty)

```

Column {.sidebar}
-----------------------------------------------------------------------

### Control

```{r}
radioButtons('yvars',
             label = 'Select a Y Variable to Plot',
             selected = 'Sepal.Width',
             choices = c('Sepal.Width', 'Petal.Length', 'Petal.Width'))
```

Column 
-----------------------------------------------------------------------

### Chart

```{r}
dset <- legend <- series <- NULL

output$chart <- ecs.render({
  # add column color
  tmp <- data.frame(Species = as.vector(unique(iris$Species)),
                    color = c("#387e78","#eeb422","#d9534f"))
  df <- iris %>% inner_join(tmp)
  p <- df %>% group_by(Species) %>% ec.init()
  p$x$opts$xAxis <- list(name='Sepal.Length', nameLocation='center')
  p$x$opts$yAxis <- list(name='Sepal.Width', nameRotate=90, nameLocation='center')

	# save valuable data from presets, reuse later
	dset   <<- p$x$opts$dataset
	legend <<- p$x$opts$legend
	series <<- p$x$opts$series
  p
})

observeEvent(input$yvars, {
  p <- ecs.proxy('chart')

	p$x$opts <- list(
    xAxis = list(name='Sepal.Length', nameLocation='center'),
		yAxis = list(name=input$yvars, nameRotate=90, nameLocation='center'),
		dataset = dset,
		legend = legend,
		series = lapply(series, function(s) {
			s$encode = list(y=input$yvars, x='Sepal.Length'); s })
	)
	p %>% ecs.exec('p_replace')
})

ecs.output("chart")

```

echarty solution. Original code from @EKtheSage.