e_mark_line function query w.r.t given example "echarts4r" Package

[parth77]

Dear friends,
Please review the following code. It produces line race plot (line race with titles).

My question is how a list containing no numerical value when assigned to map mark lines generates numbers.
I would really appreciate if you can explain especially the e_mark_line part and its use.

Thanks in advance.
Parth

CODE

max <- list(
name = "Max",
type = "max"
)

min <- list(
name = "Min",
type = "min"
)

avg <- list(
type = "average",
name = "AVG"
)

mtcars |>
e_charts(mpg) |>
e_line(wt) |>
e_line(drat) |>
e_line(cyl) |>
e_mark_point("wt", data = max) |>
e_mark_point(c("cyl", "drat"), data = min) |>
e_mark_line(data = avg) |> # applies to all
e_mark_area(
serie = "wt",
data = list(
list(xAxis = "min", yAxis = "min"),
list(xAxis = "max", yAxis = "max")
)
)

[technocrat]

Here's [a reprex. See the FAQ](https://forum.posit.co/t/faq-how-to-do-a-minimal-

To illustrate the question

@parth77

list containing no numerical value when assigned to map mark lines generates numbers

is because e_mark_line is an argument to the echarts4r object class derived from mtcars, which encapsulates all of the numeric data in mtcars. This illustrates one of the pitfalls of the convenient |> and %>% operators, which is that objects can be implicit.

The signature for e_mark_line

e_mark_line(
  e,
  serie = NULL,
  data = NULL,
  ...,
  title = NULL,
  title_position = NULL
)

takes e as its required argument (e is an echart4r object), and that is hidden from view by

@parth77

e_mark_line(data = avg) |

which is, in effect, e as if

e_mark_line(e, data = avg_)

Here's an interior view of e for these data

library(echarts4r)
str(e_charts(mtcars,mpg))
#> List of 8
#>  $ x            :List of 10
#>   ..$ theme   : chr ""
#>   ..$ tl      : logi FALSE
#>   ..$ draw    : logi TRUE
#>   ..$ renderer: chr "canvas"
#>   ..$ mapping :List of 3
#>   .. ..$ x        : chr "mpg"
#>   .. ..$ x_class  : chr "numeric"
#>   .. ..$ include_x: logi TRUE
#>   ..$ events  : list()
#>   ..$ buttons : list()
#>   ..$ opts    :List of 2
#>   .. ..$ yAxis:List of 1
#>   .. .. ..$ :List of 1
#>   .. .. .. ..$ show: logi TRUE
#>   .. ..$ xAxis:List of 1
#>   .. .. ..$ :List of 1
#>   .. .. .. ..$ type: chr "value"
#>   ..$ data    :List of 1
#>   .. ..$ :'data.frame':  32 obs. of  11 variables:
#>   .. .. ..$ mpg : num [1:32] 10.4 10.4 13.3 14.3 14.7 15 15.2 15.2 15.5 15.8 ...
#>   .. .. ..$ cyl : num [1:32] 8 8 8 8 8 8 8 8 8 8 ...
#>   .. .. ..$ disp: num [1:32] 472 460 350 360 440 ...
#>   .. .. ..$ hp  : num [1:32] 205 215 245 245 230 335 180 150 150 264 ...
#>   .. .. ..$ drat: num [1:32] 2.93 3 3.73 3.21 3.23 3.54 3.07 3.15 2.76 4.22 ...
#>   .. .. ..$ wt  : num [1:32] 5.25 5.42 3.84 3.57 5.34 ...
#>   .. .. ..$ qsec: num [1:32] 18 17.8 15.4 15.8 17.4 ...
#>   .. .. ..$ vs  : num [1:32] 0 0 0 0 0 0 0 0 0 0 ...
#>   .. .. ..$ am  : num [1:32] 0 0 0 0 0 1 0 0 0 1 ...
#>   .. .. ..$ gear: num [1:32] 3 3 3 3 3 5 3 3 3 5 ...
#>   .. .. ..$ carb: num [1:32] 4 4 4 4 4 8 3 2 2 4 ...
#>   ..$ dispose : logi TRUE
#>  $ width        : NULL
#>  $ height       : NULL
#>  $ sizingPolicy :List of 7
#>   ..$ defaultWidth : chr "100%"
#>   ..$ defaultHeight: NULL
#>   ..$ padding      : num 0
#>   ..$ fill         : NULL
#>   ..$ viewer       :List of 6
#>   .. ..$ defaultWidth : NULL
#>   .. ..$ defaultHeight: NULL
#>   .. ..$ padding      : NULL
#>   .. ..$ fill         : logi TRUE
#>   .. ..$ suppress     : logi FALSE
#>   .. ..$ paneHeight   : NULL
#>   ..$ browser      :List of 5
#>   .. ..$ defaultWidth : NULL
#>   .. ..$ defaultHeight: NULL
#>   .. ..$ padding      : NULL
#>   .. ..$ fill         : logi TRUE
#>   .. ..$ external     : logi FALSE
#>   ..$ knitr        :List of 3
#>   .. ..$ defaultWidth : NULL
#>   .. ..$ defaultHeight: NULL
#>   .. ..$ figure       : logi FALSE
#>  $ dependencies : NULL
#>  $ elementId    : NULL
#>  $ preRenderHook:function (e)  
#>  $ jsHooks      : list()
#>  - attr(*, "class")= chr [1:2] "echarts4r" "htmlwidget"
#>  - attr(*, "package")= chr "echarts4r"

^{Created on 2023-02-17 with reprex v2.0.2}

[parth77]

How can I use e_mark_line or e_mark_p function to have running marker with the other than avg, min or max. For eg. what I if want to use category labels as line marker?

Example.
library(babynames)

df = babynames %>% filter(name %in% c("Mary"), sex == "F")
df$year = as.factor(df$year)

Average marker

df %>% group_by(name) %>%
e_chart(x = year, color = c("#984EA3")) %>%
e_line(serie = n) %>%
e_legend(show = F) %>%
e_mark_p(type = "line", data = list(type = "average"))

The line represents the constant average. Here I wanted to display name value ("Mary").
Is this possible to achieve?

[technocrat]

@parth77

Is this possible to achieve?

I don't see a way in echart4r. It could be done in {ggplot2} if the animation is not required.

[parth77]

Okay,
Thank you for the quick reply.

Regards,
PT