Using geom_function() in ggplot

Question

This is my data frame and my ggplot:

df_f <- tibble(
    seq_n = seq(1, 11, 1),
    top_white_values = c(1970, 1985, 1963, 1949, 1943, 1941, 1930, 1942, 1985, 1955, 1971)
)

ggplot(data = df_f) + 
    geom_point(aes(x = seq_n, y = top_white_values)) +
    geom_text(aes(x = seq_n, y = top_white_values, label = top_white_values))

I need to connect the dots labeled by year to the x-axis numbers but I need to use geom_function(). I would like to have some rounded functions like x^2, x^2, x^(1/2).

This is the result I want to achieve:

PS: Is there anything like a "Math Function Generator" that could help me to know the function related to the draw I did in this graphics? For example, I draw a function like the above and the App generates to me the mathematical function similar to this shape/draw?

Brian Montgomery · Accepted Answer · 2021-08-30 00:23:34Z

4

These curves look like tangent functions, so:

library(ggplot2)
df_f <- data.frame(
  seq_n = seq(1, 11, 1),
  top_white_values = c(1970, 1985, 1963, 1949, 1943, 1941, 1930, 1942, 1985, 1955, 1971)
)

my_tan <- function(x0, x1, y1){
  ymin <- layer_scales(last_plot())$y$range$range[1]
  ymax <- layer_scales(last_plot())$y$range$range[2]
  mult <- (ymax - ymin)/10
  function(x) mult * tan(pi/1.15 * (x - (x0 + x1) / 2) / (x1 - x0)) + (y1 + ymin)/2
}

plt <- ggplot(data = df_f) + 
  geom_point(aes(x = seq_n, y = top_white_values)) +
  geom_text(aes(x = seq_n, y = top_white_values, label = top_white_values))
plt + geom_function(fun = my_tan(3, 9, 1985), xlim = c(3, 9)) + 
  geom_function(fun = my_tan(9, 2, 1985), xlim = c(2, 9))

Which gives:

answered Aug 30, 2021 at 0:23

Brian Montgomery

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