transition_layers.md

transistion_layers

Adam Gruer + Saskia Freytag 22/11/2018

transistion_layers()

what do I think it will do?

I think it will add a frame for each geom_ I add to the plot.

What does the help say

?transition_layers

Build up a plot, layer by layer

This transition gradually adds layers to the plot in the order they have been defined. By default prior layers are kept for the remainder of the animation, but they can also be set to be removed as the next layer enters.

Usage

transition_layers(layer_length, transition_length, keep_layers = TRUE, from_blank = TRUE, layer_names = NULL)

First attempt

Add three layers: geom_point and geom_histogram and a geom_bar. It did do as I expected.

I still struggle to understand the layer_length and transition_length beyond them being relative times.

 ggplot(mtcars ) + 
  geom_point(aes(disp, mpg), colour = "purple", size = 3)  +
  geom_histogram(aes(disp)) +
  geom_bar(aes(cyl))+
  transition_layers(layer_length = 1, transition_length = 1, keep_layers = TRUE)

## `stat_bin()` using `bins = 30`. Pick better value with `binwidth`.

It is very literal. ggplot(mtcars) is a layer, albeit an uninteresting one. However one of the arguments from_blank which defaults to TRUE can be changed to FALSE so as to not show this first layer.

Here I show the effect of not showing the first ‘blank’ layer.

 ggplot(mtcars ) + 
  geom_point(aes(disp, mpg), colour = "purple", size = 3)  +
  geom_histogram(aes(disp)) +
    geom_bar(aes(cyl))+
  transition_layers(layer_length = 1, transition_length = 1, keep_layers = TRUE, from_blank =  FALSE ) 

## `stat_bin()` using `bins = 30`. Pick better value with `binwidth`.

I can choose not to keep each layer as I animate by setting keep_layers = FALSE.

 ggplot(mtcars ) + 
  geom_point(aes(disp, mpg), colour = "purple", size = 3)  +
  geom_histogram(aes(disp)) +
    geom_bar(aes(cyl))+
  transition_layers(layer_length = 1, transition_length = 1, keep_layers = FALSE, from_blank =  FALSE ) 

## `stat_bin()` using `bins = 30`. Pick better value with `binwidth`.

I can supply layer names to be used as label literals.

ggplot(mtcars ) + 
  geom_point(aes(disp, mpg), colour = "purple", size = 3)  +
  geom_histogram(aes(disp)) +
    geom_bar(aes(cyl)) +
  labs(title = "{closest_layer}") +
  transition_layers(layer_length = 1, transition_length = 1, keep_layers = FALSE, from_blank =  FALSE, layer_names  = c("geom_point(disp,mpg)",
                                                                                                                        "geom_histogram(disp)",
                                              "geom_bar(cyl)")
                    ) 

## `stat_bin()` using `bins = 30`. Pick better value with `binwidth`.

Simulate some stuff

In the next bit we simulate a density and show which points we sample. Then we show what distribution they would form. To do this we can set the parameter keep_layers = TRUE and pass layer_length a vector of times we want to see each layer for.

sim <- data.frame(x = rnorm(10000, 0, 1), 
  sampled = sample(c("TRUE", rep("FALSE", 9)), 10000, replace = TRUE),
  index= 1:10000)

sim <- sim %>% mutate(x_bins =cut(x, 30)) %>% mutate(x_bins2 = as.numeric(x_bins))
sim <- sim[order(sim$x_bins2), ]
sim$y <- 1
sim$y <- unlist(lapply(split(sim$y, sim$x_bins2), cumsum)) 

sim_1 <- sim %>% filter(sampled==TRUE)
sim_1 <- sim_1[order(sim_1$x_bins2), ]
sim_1$y_1 <- 1
sim_1$y_1 <- unlist(lapply(split(sim_1$y_1, sim_1$x_bins2), cumsum)) 

ggplot(sim, aes(x_bins, y)) + geom_point() + 
  geom_point(data=sim_1, aes(x_bins, y), col="grey") +
  geom_point(data=sim_1, aes(x_bins, y_1), col="hotpink") +
  theme(axis.text.x = element_blank()) +
   transition_layers(layer_length = c(1, 2, 2), transition_length = 1, 
                     keep_layers = TRUE, from_blank = FALSE, 
                     layer_names  = c("Density", rep("Sampled", 2)))