PLotly chart with 2 y-axes display 2 x-axes as well one over the other

Question

I have created a plotly chart with 2 y-axes. Im wondering why they seem to have 2 x-axes though. Its like one is over the other.

    df2<-structure(list(year = c(1951, 1954, 1955, 1957, 1958, 1960, 1961, 
    1962, 1963, 1964, 1965, 1967, 1968, 1969, 1970, 1971, 1972, 1973, 
    1974, 1975, 1976, 1977, 1979, 1980, 1981, 1982, 1983, 1984, 1985, 
    1986, 1988, 1989, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 
    1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 
    2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019), 
        Scope = c(4, 3, 5, 27, 6, 13, 6, 6, 24, 1, 21, 24, 32, 57, 
        18, 1, 43, 39, 8, 58, 68, 78, 7, 20, 26, 4, 12, 19, 8, 37, 
        35, 51, 209, 478, 395, 355, 453, 457, 262, 148, 196, 180, 
        367, 283, 360, 414, 175, 330, 314, 446, 428, 163, 213, 165, 
        307, 231, 53, 189, 18, 104, 39), count = c(1, 1, 1, 1, 2, 
        4, 1, 2, 2, 1, 3, 2, 3, 6, 4, 1, 9, 6, 3, 4, 5, 5, 2, 3, 
        2, 2, 2, 4, 3, 3, 5, 5, 14, 26, 18, 25, 23, 26, 19, 13, 12, 
        13, 20, 22, 24, 25, 14, 21, 15, 22, 18, 8, 13, 6, 11, 9, 
        5, 5, 1, 3, 1), fiveYears = c("1951-1955", "1951-1955", "1951-1955", 
        "1957-1961", "1957-1961", "1957-1961", "1957-1961", "1962-1965", 
        "1962-1965", "1962-1965", "1962-1965", "1967-1971", "1967-1971", 
        "1967-1971", "1967-1971", "1967-1971", "1972-1977", "1972-1977", 
        "1972-1977", "1972-1977", "1972-1977", "1972-1977", "1979-1982", 
        "1979-1982", "1979-1982", "1979-1982", "1983-1986", "1983-1986", 
        "1983-1986", "1983-1986", "1988-1992", "1988-1992", "1988-1992", 
        "1988-1992", "1993-1998", "1993-1998", "1993-1998", "1993-1998", 
        "1993-1998", "1993-1998", "1999-2003", "1999-2003", "1999-2003", 
    "1999-2003", "1999-2003", "2004-2008", "2004-2008", "2004-2008", 
        "2004-2008", "2004-2008", "2009-2013", "2009-2013", "2009-2013", 
        "2009-2013", "2009-2013", "2014-2019", "2014-2019", "2014-2019", 
        "2014-2019", "2014-2019", "2014-2019"), Scope_min = c(3, 
        3, 3, 6, 6, 6, 6, 1, 1, 1, 1, 1, 1, 1, 1, 1, 8, 8, 8, 8, 
        8, 8, 4, 4, 4, 4, 8, 8, 8, 8, 35, 35, 35, 35, 148, 148, 148, 
        148, 148, 148, 180, 180, 180, 180, 180, 175, 175, 175, 175, 
        175, 163, 163, 163, 163, 163, 18, 18, 18, 18, 18, 18), Scope_max = c(5, 
        5, 5, 27, 27, 27, 27, 24, 24, 24, 24, 57, 57, 57, 57, 57, 
        78, 78, 78, 78, 78, 78, 26, 26, 26, 26, 37, 37, 37, 37, 478, 
        478, 478, 478, 457, 457, 457, 457, 457, 457, 367, 367, 367, 
        367, 367, 446, 446, 446, 446, 446, 428, 428, 428, 428, 428, 
        231, 231, 231, 231, 231, 231)), class = c("tbl_df", "tbl", 
    "data.frame"), row.names = c(NA, -61L))

old.y <- list(
  side = "left",
  title = "Scope"
)

new.y <- list(
  overlaying = "y",
  side = "right",
  title = "Count",
  range = c(0,500)
)

plot_ly(df2) %>%
  add_markers (x = ~fiveYears, y = ~Scope, yaxis="y1") %>%
  add_markers(x = ~fiveYears, y = ~count, yaxis = "y2") %>%
  layout(yaxis2 = new.y, yaxis = old.y, xaxis = list(title="Periods"))

Answer 1

Imposing the same axis bounds will remove the line (or rather move it down to be conterminous with the first).

old.y <- list(
  side = "left",
  title = "Scope", 
  range= c(0,500)
)

new.y <- list(
  overlaying = "y",
  side = "right",
  title = "Count",
  range = c(0,500)
)

plot_ly(df2) %>%
  add_markers (x = ~fiveYears, y = ~Scope, yaxis="y1") %>%
  add_markers(x = ~fiveYears, y = ~count, yaxis = "y2") %>%
  layout(yaxis2 = new.y, yaxis = old.y, xaxis = list(title="Periods"))

Just as a suggestion, you could even relabel the axis ticks and rescale the count variable so the counts take up the whole plotting region.

old.y <- list(
  side = "left",
  title = "Scope", 
  range= c(0,500)
)

new.y <- list(
  overlaying = "y",
  side = "right",
  title = "Count",
  range = c(0,500), 
  tickvals = c(0,100,200,300,400,500), 
  ticktext = c(0,6,12,18,24,30)
  
)

plot_ly(df2) %>%
  add_markers (x = ~fiveYears, y = ~Scope, yaxis="y1") %>%
  add_markers(x = ~fiveYears, y = ~count*16.6667, yaxis = "y2") %>%
  layout(yaxis2 = new.y, yaxis = old.y, xaxis = list(title="Periods"))