ggplot2: Secondary Y axis

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• Edit: Incrementally change existing plot (2016-11-28)

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Use parameter sec.axis of scale_y_continuous()

Simple example

sapply(c("pipeR", "ggplot2", "readr", "lubridate"), require, character.only = TRUE)

 要求されたパッケージ pipeR をロード中です 
 要求されたパッケージ ggplot2 をロード中です 
 要求されたパッケージ readr をロード中です 
 要求されたパッケージ lubridate をロード中です 

 次のパッケージを付け加えます: ‘lubridate’ 

 以下のオブジェクトは ‘package:base’ からマスクされています: 

     date 

    pipeR   ggplot2     readr lubridate 
     TRUE      TRUE      TRUE      TRUE 

Temperature and precipitation in Naha city, Okinawa, Japan (2015)

• Obtained from Japan meteorological agency

d <- read_csv("data/ggplot2-two-axis/naha.csv", skip = 5, col_names = c("Date", "Temperature", "Precipitation"), col_types = cols(col_date(format = "%Y/%m"), "d", "_", "_", "d", "_", "_", "_"), locale = locale(encoding = "SJIS"))
head(d)

Precipitation

d %>>% ggplot() + 
  geom_bar(mapping = aes(x = Date, y = Precipitation), stat = "identity") + 
  ylab("Precipitation (mm)")

Temperature

d %>>% ggplot() + 
  geom_point(mapping = aes(x = Date, y = Temperature)) + 
  geom_line(mapping = aes(x = Date, y = Temperature)) + 
  ylab(expression("Temperature ("~degree~"C)"))

Range of data

summary(d)

      Date             Temperature    Precipitation   
 Min.   :2015-01-01   Min.   :16.60   Min.   : 22.00  
 1st Qu.:2015-03-24   1st Qu.:19.82   1st Qu.: 46.88  
 Median :2015-06-16   Median :24.35   Median : 84.00  
 Mean   :2015-06-16   Mean   :23.59   Mean   :118.75  
 3rd Qu.:2015-09-08   3rd Qu.:28.02   3rd Qu.:124.38  
 Max.   :2015-12-01   Max.   :29.00   Max.   :369.00  

To set Temperature 0 – 30 and Precipitation 0 – 400, scale Precipitation by multiplying 30 / 400 to fit range of Temperature

gp1 <- d %>>% ggplot() + 
  geom_bar(mapping = aes(x = Date, y = Precipitation * 30 / 400), stat = "identity") + 
  geom_point(mapping = aes(x = Date, y = Temperature)) + 
  geom_line(mapping = aes(x = Date, y = Temperature)) + 
  scale_y_continuous(name = expression("Temperature ("~degree~"C)"), limits = c(0, 30))
gp1

Scale first Y axis by multiplying 400 / 300 to create secondary Y axis for Precipitation

• scale_y_continuous(sec.axis = sec_axis(~ . * 400 / 30))

gp1 <- gp1 %+% scale_y_continuous(name = expression("Temperature ("~degree~"C)"), sec.axis = sec_axis(~ . * 400 / 30 , name = "Precipitation (mm)"), limits = c(0, 30))

Scale for 'y' is already present. Adding another scale for 'y', which will replace the existing scale.

gp1

Final plot

d %>>% ggplot() + 
  geom_bar(mapping = aes(x = Date, y = Precipitation * 30 / 400), stat = "identity", colour = gray(0.5), fill = gray(0.5)) + 
  geom_line(mapping = aes(x = Date, y = Temperature)) + 
  geom_point(mapping = aes(x = Date, y = Temperature), size = 3, shape = 21, fill = "white") + 
  scale_x_date(name = "Month", breaks = seq.Date(as.Date("2015-01-01"), as.Date("2015-12-31"), by = "1 month"), labels = function(date){return(month(date, label = TRUE))}) + 
  scale_y_continuous(
    name = expression("Temperature ("~degree~"C)"), 
    sec.axis = sec_axis(~ . * 400 / 30 , name = "Precipitation (mm)"), 
    limits = c(0, 30)) + 
  theme_bw() + 
  theme(
    panel.grid.major = element_blank(), 
    panel.grid.minor = element_blank()
  )

Complex example: data contains negative values

Temperature and precipitation in Kushiro city, Hokkaido, Japan (2015)

• Obtained from Japan meteorological agency

d2 <- read_csv("data/ggplot2-two-axis/kushiro.csv", skip = 5, col_names = c("Date", "Temperature", "Precipitation"), col_types = cols(col_date(format = "%Y/%m"), "d", "_", "_", "d", "_", "_", "_"), locale = locale(encoding = "SJIS"))
head(d2)

Precipitation

d2 %>>% ggplot() + 
  geom_bar(mapping = aes(x = Date, y = Precipitation), stat = "identity") + 
  ylab("Precipitation (mm)")

Temperature

d2 %>>% ggplot() + 
  geom_point(mapping = aes(x = Date, y = Temperature)) + 
  geom_line(mapping = aes(x = Date, y = Temperature)) + 
  ylab(expression("Temperature ("~degree~"C)"))

summary(d2)

      Date             Temperature     Precipitation   
 Min.   :2015-01-01   Min.   :-3.300   Min.   : 37.00  
 1st Qu.:2015-03-24   1st Qu.: 1.300   1st Qu.: 56.00  
 Median :2015-06-16   Median : 7.950   Median : 82.75  
 Mean   :2015-06-16   Mean   : 7.742   Mean   : 96.50  
 3rd Qu.:2015-09-08   3rd Qu.:13.725   3rd Qu.:107.75  
 Max.   :2015-12-01   Max.   :18.400   Max.   :242.00  

To set Temperature -5 – 20 and Precipitation 0 – 250: * Scale Precipitation by multiplying 1/10 to fit range of Temperature, after that, scale Precipitation by adding -5 * Scale first Y axis by adding +5, after that, scale Precipitation by multiplying 10 to create second Y axis for Precipitation

gp2 <- d2 %>>% ggplot() + 
  geom_bar(mapping = aes(x = Date, y = Precipitation / 10 - 5), stat = "identity", colour = gray(0.5), fill = gray(0.5)) + 
  geom_line(mapping = aes(x = Date, y = Temperature)) + 
  geom_point(mapping = aes(x = Date, y = Temperature), size = 3, shape = 21, fill = "white") + 
  scale_x_date(name = "Month", breaks = seq.Date(as.Date("2015-01-01"), as.Date("2015-12-31"), by = "1 month"), labels = function(date){return(month(date, label = TRUE))}) + 
  scale_y_continuous(
    name = expression("Temperature ("~degree~"C)"), 
    sec.axis = sec_axis(~ (. + 5) * 10 , name = "Precipitation (mm)"), 
    limits = c(-5, 20)) + 
  theme_bw() + 
  theme(
    panel.grid.major = element_blank(), 
    panel.grid.minor = element_blank()
  )
gp2

geom_bar() start from 0, use geom_segment()

gp2$layers[[1]] <- geom_segment(mapping = aes(x = Date, y = Precipitation / 10 - 5, xend = Date, yend = -5), size = 11, lineend = "butt", colour = gray(0.5))
gp2

devtools::session_info()

Session info ----------------------------------------------------------------------------------------------------------

 setting  value                       
 version  R version 3.3.2 (2016-10-31)
 system   x86_64, mingw32             
 ui       RStudio (1.0.44)            
 language (EN)                        
 collate  Japanese_Japan.932          
 tz       Asia/Tokyo                  
 date     2016-11-29                  

Packages --------------------------------------------------------------------------------------------------------------

 package    * version date       source        
 assertthat   0.1     2013-12-06 CRAN (R 3.2.1)
 colorspace   1.2-7   2016-10-11 CRAN (R 3.3.2)
 devtools     1.12.0  2016-06-24 CRAN (R 3.3.1)
 digest       0.6.10  2016-08-02 CRAN (R 3.3.1)
 ggplot2    * 2.2.0   2016-11-11 CRAN (R 3.3.2)
 gtable       0.2.0   2016-02-26 CRAN (R 3.2.5)
 knitr        1.15    2016-11-09 CRAN (R 3.3.2)
 labeling     0.3     2014-08-23 CRAN (R 3.2.1)
 lazyeval     0.2.0   2016-06-12 CRAN (R 3.2.5)
 lubridate  * 1.6.0   2016-09-13 CRAN (R 3.2.5)
 magrittr     1.5     2014-11-22 CRAN (R 3.2.1)
 memoise      1.0.0   2016-01-29 CRAN (R 3.2.3)
 munsell      0.4.3   2016-02-13 CRAN (R 3.2.5)
 pipeR      * 0.6.1.3 2016-04-04 CRAN (R 3.3.1)
 plyr         1.8.4   2016-06-08 CRAN (R 3.2.5)
 Rcpp         0.12.7  2016-09-05 CRAN (R 3.2.5)
 readr      * 1.0.0   2016-08-03 CRAN (R 3.2.5)
 scales       0.4.1   2016-11-09 CRAN (R 3.3.2)
 stringi      1.1.2   2016-10-01 CRAN (R 3.3.2)
 stringr      1.1.0   2016-08-19 CRAN (R 3.2.5)
 tibble       1.2     2016-08-26 CRAN (R 3.2.5)
 withr        1.0.2   2016-06-20 CRAN (R 3.2.5)