How to use ggplot in a loop with computed parameters?

Question

I am trying to produce a variable number of rectangles (layers) in a ggplot of a zoo object. I would like to do this in a loop since I do not know ahead of time how many rectangles I will need. Here is a toy example.

library("zoo")
library("ggplot2")
set.seed(1)
y <- runif(50, min = 1, max = 2)
start <- as.numeric(as.Date("2018-01-01"))
x <- as.Date(start:(start + 49))
x.zoo <- zoo(y, order.by = x)
## Fill areas
bars <- data.frame(start = c(x[5], x[20], x[35]),
                end = c(x[10], x[25], x[40]))

I can plot these manually with this code:

## Plot manually
print(autoplot.zoo(x.zoo, facets = NULL) +
        geom_rect(aes(xmin = bars[1,1],
                  xmax = bars[1,2], ymin = -Inf, ymax = Inf),
                  fill = "pink", alpha = 0.01) +
        geom_rect(aes(xmin = bars[2,1],
                  xmax = bars[2,2], ymin = -Inf, ymax = Inf),
                  fill = "pink", alpha = 0.01) +
        geom_rect(aes(xmin = bars[3,1],
                  xmax = bars[3,2], ymin = -Inf, ymax = Inf),
                  fill = "pink", alpha = 0.01))

This gives me this desired image:

I tried using the loop below but it only plots the last bar. How do I do this??

## This didn't work but illustrates what I am trying to do
p =  autoplot.zoo(x.zoo, facets = NULL)
for(i in 1:3) {
  p = p + geom_rect(aes(xmin = bars[i,1],
                    xmax = bars[i,2], ymin = -Inf, ymax = Inf),
                    fill = "pink", alpha = 0.01)

}
print(p)

Sorry - I misspoke. This incarnation of the loop only plots the last bar and not the first two. It does NOT throw an error — Ernie
– Ernie, Commented Mar 20, 2018 at 14:27
This isn't related to your problem, but as.Date() give me an error unless I supply an origin = parameter specifying how many days to start counting from. — divibisan
– divibisan, Commented Mar 20, 2018 at 14:30
@divibisan, OP used the zoo package. @Ernie, please include the important packages. — hpesoj626
– hpesoj626, Commented Mar 20, 2018 at 14:32

Richard Telford · Accepted Answer · 2018-03-20 14:32:05Z

4

You don't need a loop. geom_rect is vectorised

autoplot.zoo(x.zoo, facets = NULL) +
  geom_rect(aes(xmin = start, xmax = end, ymin = -Inf, ymax = Inf), data = bars, fill = "pink", alpha = 0.4, inherit.aes = FALSE)

answered Mar 20, 2018 at 14:32

Richard Telford

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hpesoj626 · Accepted Answer · 2018-03-20 14:28:44Z

1

One way to avoid the for loop is to convert x.zoo into a data.frame and map the data to geom_line. This way, you can map the bars data to geom_rect separately.

dat <- data.frame(index = index(x.zoo), data.frame(x.zoo))

ggplot() + 
  geom_rect(data = bars, aes(xmin = start, xmax = end, ymin =-Inf, ymax = Inf), fill = 'pink', alpha = .5) +
  geom_line(data=dat, aes(x = index, y = x.zoo))

answered Mar 20, 2018 at 14:28

hpesoj626

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