如何使用ggplot在绘图上写入某些参数的值

Question

I want to resolve the following bit for a shiny app I am developing.

My question is: How I can write the values for AUC, Cmax and their standard deviations on a ggplot.

An example data looks like this:

data <-
ID   TIME   DV   AUC   Cmax   SD_AUC SD_Cmax
1     0     0    1.4   4.1    0.8    0.5
1     1     0.5  1.4   4.1    0.8    0.5
1     2     2    1.4   4.1    0.8    0.5
1     3     4    1.4   4.1    0.8    0.5
1     4     6    1.4   4.5    0.8    0.5
1     5     3    1.4   4.5    0.8    0.5
1     6     2    1.4   4.5    0.8    0.5
1     7     1    1.4   4.5    0.8    0.5

Code for plotting:

plotobj <- ggplot(data)
plotobj <- plotobj + geom_line(aes(x=TIME, y=DV), colour="red", size=1)

The plot should be something close to this: (I did the plot in excel for demonstration only)

How can I achieve this in R using ggplot ?

Note: The values for AUC, Cmax and SD changes (updates) depending on certain parameters in the shinyapp. So, the ggplot code should be general and takes whatever the value in the corresponding column is.

I used this code for AUC as an example:

plotobj <- plotobj + annotate("text", x = 6, y = 5, label = "median AUC", colour = "red", size = 6)

but couldn't get the numbers there.

Answer 1

Let's excerpt some of your data:

AUC   Cmax   SD_AUC SD_Cmax
1.4   4.1    0.8    0.5
1.4   4.1    0.8    0.5
1.4   4.1    0.8    0.5
1.4   4.1    0.8    0.5
1.4   4.5    0.8    0.5
1.4   4.5    0.8    0.5

Pretty repetitive and boring! This is unnecessary. Pick your favorite data transformation method and turn it into this:

metrics = structure(list(Label = structure(c(1L, 3L, 2L, 4L),
    Label = c("Median AUC", "Median Cmax", "SD AUC", "SD Cmax"), class = "factor"),
    Value = c(1.4, 0.8, 4.5, 0.5)),
    .Names = c("Label", "Value"),
    class = "data.frame", row.names = c(NA, -4L))

metrics

        Label  Value
 'Median AUC'    1.4
     'SD AUC'    0.8
'Median Cmax'    4.5
    'SD Cmax'    0.5

Really, you can go straight to the next step if you'd prefer, but the data above should be easy to get to and a great starting place.

annotation = paste(metrics$Label, metrics$Value, sep = " = ", collapse = "\n")

Then you can add to your plot object:

annotate(geom = "text" label = annotation, x = 6, y = 5)

You'll have to play with the x and y values to position it nicely.

Answer 2

Since the values for AUC and Cmax updates every time you change a parameter in the Shiny app then using geom_text is the way to go. I can see the logic behind Gregor's answer above but using annotate can add text but not numbers that are changing upon updating the Shiny app.

The job requested by the question can be done using the following:

     yscalemax <- max(data$DV)      #set values for plot limits
      xscalemax <- max(data$TIME)*1.1
      plotobj <- ggplot(data)
      plotobj <- plotobj + geom_line(aes(x=TIME, y=DV), colour="red", size=1)
      plotobj <- plotobj + stat_summary(aes(x=TIME, y=DV), fun.y=median, geom="line", colour="red", size=1)
      plotobj <- plotobj + geom_text(aes(label = paste("AUC =",AUC)), x = xscalemax*0.8, y = yscalemax*0.6, colour = "red", size = 6)
      plotobj <- plotobj + geom_text(aes(label = paste("SD AUC =",SD_AUC)), x = xscalemax*0.8, y = yscalemax*0.55, colour = "red", size = 6)

And so on for Cmax. In this case the position of the text will be adjusted depending on max(DV) and max(TIME) with the calculated values for AUC , SD_AUC sticked on the plot.