Ribbon is a horizontal band of colors that runs through the chart. It
can be useful to visualize categorical variables (http://en.wikipedia.org/wiki/Categorical_variable) that
change over time (along the x-axis). For example multiple states of
economy like “bust”, “recession”, “recovery”, “boom” can be encoded as
[0, 1, 2, 3] respectively (or normalized as
[0, 0.33, 0.66, 1]) and assigned colors
["red", "orange", "green", "purple"].
The following chart contains a colored ribon at the bottom. The
position of ribbon is set with top and bottom
parameters of dyRibbon() function, 0 means the
very bottom of chart while 1 represents a very top.
## Loading required package: xts## Loading required package: zoo##
## Attaching package: 'zoo'## The following objects are masked from 'package:base':
##
## as.Date, as.Date.numeric## Loading required package: TTR## Registered S3 method overwritten by 'quantmod':
## method from
## as.zoo.data.frame zoo
getSymbols("SPY", from = "2016-12-01", auto.assign = TRUE)## [1] "SPY"
difference <- SPY[, "SPY.Open"] - SPY[, "SPY.Close"]
decreasing <- which(difference < 0)
increasing <- which(difference > 0)
dyData <- SPY[, "SPY.Close"]
ribbonData <- rep(0, nrow(dyData))
ribbonData[decreasing] <- 0.5
ribbonData[increasing] <- 1
dygraph(dyData) |>
dyRibbon(data = ribbonData, top = 0.1, bottom = 0.02)It is also possible to feed ribbon with data using a parser written
in JavaScript. Parser has the following signature
function (rawData, dygraphInstance) and must return an
array. The following example uses such parser to make up a ribbon, also
it uses custom palette:
parser <- "function(rawData) {
var openIdx = 1;
var closeIdx = 4;
var ribbonData = [];
for (var i = 0; i < rawData.length; i++) {
var row = rawData[i];
var open = row[openIdx];
var close = row[closeIdx];
if (open < close) {
ribbonData.push(0.5);
} else if (open > close) {
ribbonData.push(1);
} else {
ribbonData.push(0);
}
}
return ribbonData;
}"
dygraph(SPY[, c("SPY.Open", "SPY.High", "SPY.Low", "SPY.Close")]) |>
dyRibbon(
parser = parser,
palette = c("#efefef", "#ffe6e6", "#ccebd6")
)