Draw a trend line using ggplot

r ggplot2 trendline
Sakura picture Sakura · Jul 16, 2016 · Viewed 92k times · Source

I used ggplot2 to draw a trend line based on my data.

Below is something I've done using spreadsheet.

But I only want to show the trend line (black line as shown in upper plot) rather than all dots as number of observation is > 20,000.

So I tried to do the same thing using ggplot2. 

fig_a <- ggplot(df1, aes(data_x, data_y ))
fig_a + stat_smooth(method=lm)
fig_a + stat_smooth(method=gam)

Apparently it does not work well, anyone can help?

Why it gives so many lines rather than single trend line?

Answer

milan picture milan · Jul 16, 2016

You can do the following. Add + geom_smooth(method = "lm") to your ggplot script.

Example using built-in data 

ggplot(mpg, aes(displ, hwy)) + geom_point() + geom_smooth(method = "lm")

enter image description here

Related questions

Adding a simple lm trend line to a ggplot boxplot

When adding a linear model trend line to a boxplot using standard R graphics I use: boxplot(iris[,2]~iris[,1],col="LightBlue",main="Quartile1 (Rare)") modelQ1<-lm(iris[,2]~iris[,1]) abline(modelQ1,lwd=2) However, when using this in ggplot2: a <…

Read More
Creating a line chart in r for the average value of groups

I'm trying to create simple line charts with r that connect data points the average of groups of respondents (would also nive to lable them or distinguish them in diferent colors etc.) My data is in long format and sorted …

Read More
Add Regression Line ggplot for Only Certain Groups

I want to add trendlines to my ggplot, but only for the significant relations. Now geom_smooth or stat_smooth adds trendlines for each group, but I want to specify which groups get a trendline and which don't. Below an …

Read More