Create a ggplotly object with a subtitle

Question

I'm plotting a Scatterplot with ggplot() as follows:

library(data.table)
library(plotly)
library(ggplot2)
library(lubridate)

dt.allData <- data.table(date = seq(as.Date('2020-01-01'), by = '1 day', length.out = 365),
                         DE = rnorm(365, 4, 1), Austria = rnorm(365, 10, 2), 
                         Czechia = rnorm(365, 1, 2), check.names = FALSE)

## Calculate Pearson correlation coefficient: ##
corrCoeff <- cor(dt.allData$Austria, dt.allData$DE,  method = "pearson", use = "complete.obs")
corrCoeff <- round(corrCoeff, digits = 2)

## Linear regression function extraction by creating linear model: ##
regLine <- lm(DE ~ Austria, data = dt.allData)

## Extract k and d values for the linear function f(x) = kx+d: ##
k <- round(regLine$coef[2], digits = 5)
d <- round(regLine$coef[1], digits = 2)
linRegFunction <- paste0("y = ", d, " + (", k, ")x")

## PLOT: ##
p1 <- ggplot(data = dt.allData, aes(x = Austria, y = DE, 
                                    text = paste("Date: ", date, '\n',
                                                 "Austria: ", Austria, "MWh/h", '\n',
                                                 "DE: ", DE, "\u20ac/MWh"),
                                    group = 1)
      ) +
      geom_point(aes(color = ifelse(date >= now()-weeks(5), "#419F44", "#F07D00"))) +
      scale_color_manual(values = c("#F07D00", "#419F44")) +
      geom_smooth(method = "lm", se = FALSE, color = "#007d3c") +
      annotate("text", x = 10, y = 10,
               label = paste("\u03c1 =", corrCoeff, '\n',
                             linRegFunction), parse = TRUE) +
      theme_classic() +
      theme(legend.position = "none") +
      theme(panel.background = element_blank()) +
      xlab("Austria") +
      ylab("DE")+
      ggtitle("DE vs Austria") +
      theme(plot.title = element_text(hjust = 0.5, face = "bold"))

# Correlation plot converting from ggplot to plotly: #
plot <- plotly::ggplotly(p1, tooltip = "text")

which gives the following plot here:

I use annotate() to represent the correlation coefficient and the regression function. I define the x and y coordinates manually so that the text output is displayed in the middle at the top. Since I have some of such data tables dt.allData that have different axis scalings, I would like to define in the plot that the text should always be displayed in the middle at the top, depending on the axis scaling without defining x and y coordinate manually before.

could you include a list of all the packages you are working with — Cettt, Oct 30 '20 at 09:45
For those interested: I just saw, that [here](https://stackoverflow.com/a/61277897/9841389) is a related question using `sup` instead of `span`. — ismirsehregal, Oct 30 '20 at 10:56

ismirsehregal · Accepted Answer · 2021-04-30T10:28:14.713

I'd suggest ~~using ggtitle and hjust = 0.5:~~

Edit: using plotly::layout and a span tag to create the title:

library(data.table)
library(ggplot2)
library(plotly)
library(lubridate)

dt.allData <- data.table(date = seq(as.Date('2020-01-01'), by = '1 day', length.out = 365),
                         DE = rnorm(365, 4, 1), Austria = rnorm(365, 10, 2), 
                         Czechia = rnorm(365, 1, 2), check.names = FALSE)

## Calculate Pearson correlation coefficient: ##
corrCoeff <- cor(dt.allData$Austria, dt.allData$DE,  method = "pearson", use = "complete.obs")
corrCoeff <- round(corrCoeff, digits = 2)

## Linear regression function extraction by creating linear model: ##
regLine <- lm(DE ~ Austria, data = dt.allData)

## Extract k and d values for the linear function f(x) = kx+d: ##
k <- round(regLine$coef[2], digits = 5)
d <- round(regLine$coef[1], digits = 2)
linRegFunction <- paste0("y = ", d, " + (", k, ")x")

## PLOT: ##
p1 <- ggplot(data = dt.allData, aes(x = Austria, y = DE, 
                                    text = paste("Date: ", date, '\n',
                                                 "Austria: ", Austria, "MWh/h", '\n',
                                                 "DE: ", DE, "\u20ac/MWh"),
                                    group = 1)
) +
  geom_point(aes(color = ifelse(date >= now()-weeks(5), "#419F44", "#F07D00"))) +
  scale_color_manual(values = c("#F07D00", "#419F44")) +
  geom_smooth(method = "lm", formula = 'y ~ x', se = FALSE, color = "#007d3c") +
  # ggtitle(label = paste("My pretty useful title", '\n', "\u03c1 =", corrCoeff, '\n', linRegFunction)) +
  theme_classic() +
  theme(plot.title = element_text(hjust = 0.5)) +
  theme(legend.position = "none") +
  theme(panel.background = element_blank()) +
  xlab("Austria") +
  ylab("DE")

# Correlation plot converting from ggplot to plotly: #
# using span tag (directly in control of font-size):
span_plot <- plotly::ggplotly(p1, tooltip = "text") %>% layout(
    title = paste(
      '<b>My pretty useful title</b>',
      '<br><span style="font-size: 15px;">',
      '\u03c1 =<i>',
      corrCoeff,
      '</i><br>',
      linRegFunction,
      '</span>'
    ),
    margin = list(t = 100)
  )
span_plot

Edit: added the sup alternative as per this answer

# using sup tag:
sup_plot <- plotly::ggplotly(p1, tooltip = "text") %>% layout(
    title = paste(
      '<b>My pretty useful title</b>',
      '<br><sup>',
      "\u03c1 =<i>",
      corrCoeff,
      '</i><br>',
      linRegFunction,
      '</sup>'
    ),
    margin = list(t = 100)
  )
sup_plot

Here you can find some related information in the plotly docs.

Sorry, I have already a title here. This was missing in my question! — MikiK, Oct 30 '20 at 09:59
Ok, thanks for clarification. Modifiying each title with two more lines is not an option? — ismirsehregal, Oct 30 '20 at 10:01
I'll try it with a subtitle, I haven't thought of that yet. Thanks for the thought bump. — MikiK, Oct 30 '20 at 10:03
The subtitle won't work with `ggplotly`. You'd need to add the lines to the title. — ismirsehregal, Oct 30 '20 at 10:05
I see, using ```subtitle = paste("\u03c1 =", corrCoeff, '\n', linRegFunction)``` doesn't work. How can I do this, when my title should be ```bold``` the other two lines not? — MikiK, Oct 30 '20 at 10:08
You could set the title using `plotly` which lets you use some html tags - please see my edit. Another approach is shown [here](https://stackoverflow.com/a/57244563/9841389) — ismirsehregal, Oct 30 '20 at 10:12
Using your html tags in the ```plotly::layout()``` wokrs perfect! It would also have to work that the font size of the correlation coefficient and the regression function is made smaller? — MikiK, Oct 30 '20 at 10:20
Yes, also possible. You need to wrap the according lines in a `span`. See my update. — ismirsehregal, Oct 30 '20 at 10:31

BrianLang · Answer 2 · 2020-10-30T10:23:16.377

0

First I would start by seeing if something like this could help you:

annotate("text", 
         x = mean(dt.allData$Austria, na.rm = TRUE), 
         y = max(dt.allData$DE, na.rm = TRUE),
         label = paste("\u03c1 =", 
                       corrCoeff, '\n',
                       linRegFunction), 
         parse = TRUE,
         hjust = .5)

and then, in the case where you want to go through a list of x,y pairs, you'd eventually you'd want to move towards functional programming where you are passing x columns x1, x2, x3 and ycolumns y1, y2, y3 to a map function which then pulls out the relevant information from each pair and plots them.

edited Oct 30 '20 at 10:23

answered Oct 30 '20 at 09:42

BrianLang

831
4
14

Thanks, but if I have some extreme outliers, then it is not in the middle of the plot. – MikiK Oct 30 '20 at 09:56
Then let's use something that is sensitive to outliers, like the mean! – BrianLang Oct 30 '20 at 09:58
I've already tried to use ```mean()```. Nevertheless, it is never exactly centered, and it often deviates a lot. – MikiK Oct 30 '20 at 10:09
Huh. well, it works for the case that you've shared here! – BrianLang Oct 30 '20 at 10:27

Create a ggplotly object with a subtitle

2 Answers2