plot a circular segment with plotly

Question

I want to use plotly to draw a circular segment with a given centre point and radius.

I found no way in the plotly documentation and tried the following code, which works but I do not want to see the intermediate points.

My current attempt:

library(plotly)

from <- 0
to <-  180
by <- (to-from)/10

t <- seq(from*pi/180, to*pi/180 , by*pi/180)

x0 <- 1
y0 <- 1
r <- 5
y <- y0 + r*sin(t)
x <- x0 + r*cos(t)

plotly::plot_ly() %>% 
  add_trace(x=~x, y = ~y, line = list(shape = "spline"))

What I want to see:

Any hints? Is it possible to remove the intermediate points afterwards? Or plot a "perfect" circle direct with plotly? Thank you in advance!

user_13513328 · Answer

you could use a layout with circle shape:

library(plotly)
plot_ly() %>% layout(shapes = list(
                list(type = 'circle',
                     xref = 'x', x0 = -4, x1 = 6,
                     yref = 'y', y0 =  -4, y1 = 6,
                     line = list(color = 'blue'))),
                     yaxis = list(range=c(1,6.5)))

Another option to draw only one half circle is to use the line shape (with more segments : by <- (to-from)/100 ):

line <- list(
  type = "line",
  line = list(color = "blue"),
  xref = "x",
  yref = "y"
)

lines <- list()

for (i in 2:length(t)) {
  line[["x0"]] <- x[i-1]
  line[["x1"]] <- x[i]
  line[["y0"]] <- y[i-1]
  line[["y1"]] <- y[i]
  lines <- c(lines, list(line))
}

library(plotly)
plot_ly() %>% layout(shapes = lines,
                     yaxis = list(range=c(0,6.5)))

plot a circular segment with plotly

1 Answers