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Plot a panel as a unit by period heat map

Source: R/plot-panel.R
panelplot.Rd

Draws one row per individual and one column per period. With value the cells are coloured by that variable: a sequential palette with a colour bar for a numeric variable, one colour per level for a factor, character or logical variable. Without value the plot shows which periods each individual is observed in, so the gaps of an unbalanced panel stand out. Periods in which an individual is not observed, and missing values of value, are drawn in neutral grey.

Usage

panelplot(
  data,
  index,
  value = NULL,
  treat = NULL,
  labels = NULL,
  col = NULL,
  zlim = NULL,
  legend = TRUE,
  xlab = "Period",
  ylab = NULL,
  main = NULL,
  ...
)

Arguments

data

a data frame in long format

index

c(individual, time): column names; the time must be numeric when treat is given

value

optional name of the column that colours the cells; NULL (the default) shows observed versus missing periods

treat

optional name of the column with the first treated period, as in attgt() (0, NA or Inf for never-treated units)

labels

logical: show the individual labels on the left axis. The default shows them for at most 60 individuals.

col

colours: for a numeric value, the palette (default: a sequential blue palette); for a discrete value, one colour per level; without value, the colour of the observed cells

zlim

limits of the colour scale for a numeric value (default: its range)

legend

logical: add a legend (or colour bar) below the plot

xlab, ylab, main

axis labels and title (default ylab: none)

...

passed to graphics::image()

Value

a data frame with one row per individual in plotting order (id, cohort when treat is given, n_periods observed and n_missing missing values of value), invisibly

Details

With treat the individuals are sorted by treatment cohort as in treatmentplot() (earliest adopters at the top, never-treated units at the bottom), the cohorts are separated by white lines and labelled on the right with their sizes, and a black edge marks the first treated period of each cohort. Without treat the individuals are in the order of their identifiers. The unit labels are shown for at most 60 individuals by default; with many individuals the tiles are drawn as a raster.

See also

treatmentplot() for the treatment timing alone, trendplot() for the mean outcome paths

Other policy evaluation: attgt(), did(), etwfe(), eventplot(), eventstudy(), treatmentplot(), trendplot()

Examples

set.seed(1)
d <- expand.grid(id = 1:30, year = 2010:2019)
d$first <- rep(c(2013, 2015, 0), each = 10)[d$id]
d$y <- rnorm(30)[d$id] + 0.1 * (d$year - 2010) + rnorm(nrow(d), sd = 0.3)
d$y[sample(nrow(d), 15)] <- NA
# observed and missing periods of an unbalanced panel
u <- d[-sample(nrow(d), 40), ]
panelplot(u, index = c("id", "year"))

# outcome values, sorted by treatment cohort
panelplot(d, index = c("id", "year"), value = "y", treat = "first")

# a discrete variable
d$high <- d$y > 0.5
panelplot(d, index = c("id", "year"), value = "high")