error when adding lm to datetime data in ggplot2

January 27, 2022

When Trying to plot the linear regression of the data the output returns a horizontal line with a warning that the fit is rank-deficient. Can someone please explain how to display a proper linear regression?

Sample Data

ToPlot <- structure(list(Time = structure(c(1643126476.049, 1643126476.099, 
1643126476.149, 1643126476.199, 1643126476.249, 1643126476.299, 
1643126476.349, 1643126476.399, 1643126476.449, 1643126476.499, 
1643126476.549, 1643126476.599, 1643126476.649, 1643126476.699, 
1643126476.749, 1643126476.799, 1643126476.849, 1643126476.899, 
1643126476.949, 1643126476.999), class = c("POSIXct", "POSIXt"
), tzone = ""), LIN = c(112.05611159876, 112.66549348, 113.37316276144, 
113.86459976244, 114.59192652392, 115.29959580536, 115.88932020656, 
116.61664696804, 117.20637136924, 117.93369813072, 118.52342253192, 
119.13280441316, 119.8404736946, 120.54814297604, 121.15752485728, 
121.86519413872, 122.47457601996, 123.1822453014, 123.79162718264, 
124.49929646408)), row.names = 314:333, class = "data.frame")

Code:

library("ggplot2")
library("scales")

ggplot(aes(x = Time, y = LIN), data = ToPlot) + 
  geom_point() + 
  geom_line() + 
  scale_x_datetime(labels = date_format("%H:%m:%S"))+
  geom_smooth(method='lm')

>Solution :

Typically the package picks the orientation (x or y) automatically. However, when it becomes uncertain, you see that message. You don’t need to specify the formula, you can just specify the orientation.

library("ggplot2")
library("scales")

ggplot(aes(x = Time, y = LIN), data = ToPlot) + 
  geom_point() + 
  geom_line() + 
  scale_x_datetime(labels = date_format("%H:%m:%S"))+
  geom_smooth(method='lm', orientation = "y")