How to smooth the line in R ggplot without using ggalt library

Question

I have a data frame like this:

df <- data.frame( posting_year = c(2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016), value = c(492, 523, 507, 66, 58, 641, 226, 990, 555, 481) )

This is the line chart I get using this code:

ggplot(df, aes(x=posting_year , y=value)) + geom_line()

But I want a line chart with a curve line. Something like this

Thank you

See https://stackoverflow.com/questions/3480388/how-to-fit-a-smooth-curve-to-my-data-in-r — nucleaR, Dec 06 '21 at 09:42
You could use `geom_smooth` but the approximation is not exactly the one you represent here. — Maël, Dec 06 '21 at 09:55

score 1 · Answer 1 · answered Dec 06 '21 at 09:57

You can use geom_smooth here, but default you get not what you try to achieve. Default is the blue one, playing around with span gives more or less the desired result in red.

ggplot(df, aes(x = posting_year, y = value)) + geom_line() + 
  geom_smooth(method = "loess", formula = y ~ x, se = F, span = 0.75, color = "blue") + # default span
  geom_smooth(method = "loess", formula = y ~ x, se = F, span = 0.20, color = "red")

Rfanatic · Answer 2 · 2021-12-06T10:31:53.460

Try this approach that is close to what you want. You can define stat_smooth()

ggplot(df, aes(x=posting_year , y=value)) +  
  geom_line(color = 'red', size=1)+
  geom_smooth(method = "loess",
              se = FALSE,
              formula = 'y ~ x',
              span = 0.2, 
              size=1)+
              theme_bw()

Data:

df <- data.frame( posting_year = c(2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016), value = c(492, 523, 507, 66, 58, 641, 226, 990, 555, 481) )

How to smooth the line in R ggplot without using ggalt library

2 Answers2