Budget constraint graph about econocharts HOT 1 OPEN

budget(rect1, rect2, x = c(3, 5), labels = c("A", "B"))

# Data
curve2 <- data.frame(Hmisc::bezier(c(1, 3, 9),
                                   c(9, 3, 1)))
x <- curve2$x
y <- curve2$y
plot(x, y)
spl <- smooth.spline(y ~ x)
lines(spl, col = 2)

newx <- 4
pred0 <- predict(spl, x = newx, deriv = 0)
pred1 <- predict(spl, x = newx, deriv = 1)

yint <- pred0$y - (pred1$y * newx)
xint <- -yint / pred1$y

ggplot(curve2, aes(x = x, y = y)) +
  geom_line(data = data.frame(x = x, y = yint + pred1$y * x), color = "red", lwd = 2) +
  geom_line(lwd = 2) + 
  geom_point(data = data.frame(x = pred0$x, y = pred0$y), size = 3, color = "green")