How to create a Sankey plot in R?

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How to create a Sankey plot in R?, You must install the ggsankey library and modify your dataset using the package’s make_long function in order to produce a Sankey diagram in ggplot2.

The data’s columns must correspond to the stages x (current stage), next_x (next stage), node (current node), and next_node (the following node).

Keep in mind that the final stage should indicate a NA.

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Let’s install the remotes packages first,

install.packages("remotes")

Now we can install ggsankey package

remotes::install_github("davidsjoberg/ggsankey")
library(ggsankey)

Load Data

We can make use of mtcars data sets in R.

df <- mtcars %>%
  make_long(cyl, vs, am, gear, carb)
df
    x   node next_x next_node
1  cyl    6     vs         0
2   vs    0     am         1
3   am    1   gear         4
4 gear    4   carb         4
5 carb    4   <NA>        NA
6  cyl    6     vs         0

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Sankey plot with ggsankey

To construct Sankey diagrams in ggplot2, the ggsankey package includes a geom called geom_sankey.

Keep in mind that you must give a factor as the fill colour when passing the variables to aes. The theme theme_sankey is also present in the function.

Let’s load ggplot2 for graph generation

library(ggplot2)
library(dplyr)
ggplot(df, aes(x = x,
               next_x = next_x,
               node = node,
               next_node = next_node,
               fill = factor(node))) +
  geom_sankey() +
  theme_sankey(base_size = 16)

How to add labels in Sankey Plot

The package’s geom_sankey_label function lets you add labels to Sankey diagrams.

Remember to give the variable you want to display as the label inside the aes.

ggplot(df, aes(x = x,
               next_x = next_x,
               node = node,
               next_node = next_node,
               fill = factor(node),
               label = node)) +
  geom_sankey() +
  geom_sankey_label() +
  theme_sankey(base_size = 16)

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How to do Color customization in Sankey Plot

To alter how the Sankey diagram appears in R, a variety of arguments can be changed. The author of the program produced the following pictures as examples.

geom_sankey aesthetics
geom_sankey geometries
Color and fill of the Sankey plot

For instance, by adjusting the fill color palette and a few of the inputs to the geom_sankey_function, we can produce something like this.

ggplot(df, aes(x = x,
               next_x = next_x,
               node = node,
               next_node = next_node,
               fill = factor(node),
               label = node)) +
  geom_sankey(flow.alpha = 0.5, node.color = 1) +
  geom_sankey_label(size = 3.5, color = 1, fill = "white") +
  scale_fill_viridis_d(option = "A", alpha = 0.95) +
  theme_sankey(base_size = 16)

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Changing the title of the legend

Changes to the legend’s title are available, just like with other ggplot2 charts. Here are several options for action.

ggplot(df, aes(x = x,
               next_x = next_x,
               node = node,
               next_node = next_node,
               fill = factor(node),
               label = node)) +
  geom_sankey(flow.alpha = 0.5, node.color = 1) +
  geom_sankey_label(size = 3.5, color = 1, fill = "white") +
  scale_fill_viridis_d() +
  theme_sankey(base_size = 16) +
  guides(fill = guide_legend(title = "Title"))

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Removing the legend

Finally, you can adjust the Sankey plot legend’s position to “none” if you want to remove it.

ggplot(df, aes(x = x,
               next_x = next_x,
               node = node,
               next_node = next_node,
               fill = factor(node),
               label = node)) +
  geom_sankey(flow.alpha = 0.5, node.color = 1) +
  geom_sankey_label(size = 3.5, color = 1, fill = "white") +
  scale_fill_viridis_d() +
  theme_sankey(base_size = 16) +
  theme(legend.position = "none")

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The post How to create a Sankey plot in R? appeared first on Data Science Tutorials

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