How to tailor R plot axis? - r

Question

I have the following data stored in a CSV file.
NodeID,pageRank
0,0.0327814931593
1,0.384378430034
2,0.342932804288
3,0.0390870921
4,0.0808856932345
5,0.0390870921
I have read the CSV file in R and ordered pageRank values in descending order.
data <- read.csv("pagerank.csv")
data <- data[order(-data$pageRank),]
After ordering, data look following.
1 0.38437843
2 0.34293280
4 0.08088569
3 0.03908709
5 0.03908709
0 0.03278149
In the above example, the first column represents NodeID (not sequentially ordered) and the second column represents pageRank (descending order). Next I have used following command to plot the data.
plot(data$pageRank, type="o", col="red", xlab="Node Rank", ylab="PageRank Value")
The plot is showing Y-axis (pageRank values) properly. However, on the X-axis it is showing sequential numbers (0,1,2,3,4,5). Hence, instead of showing sequential number, how can I plot NodeID (1,2,4,3,5,0) on the X-axis (available in data) by maintaining pageRank's descending order. I have tried the following. However, it does not maintain pageRank's descending order.
plot(data$NodeID, data$pageRank, type="o", col="red", xlab="NodeID", ylab="PageRank Value")

Answer 1

In ggplot, we assemble the plot from layers connected with the plus operator +.
So we can start by defining the dataset to plot (data), then use the aes function to specify which variables to use for the x and y axes. Finally we tell it to plot both points and a line using this data.
library(ggplot2)
ggplot(data = data,
aes(x = NodeID, y = pageRank)) +
geom_point() +
geom_line() +
xlab('Node Rank') + ylab('PageRank Value')
Simple! I highly recommend using ggplot whenever possible over the limited and obtusely designed base R graphics.

Answer 2

You can use fct_reorder from the forcats package to do the ordering for you. See also this.
library(magrittr)
library(tidyverse)
library(forcats)
txt <- "NodeID,pageRank
0,0.0327814931593
1,0.384378430034
2,0.342932804288
3,0.0390870921
4,0.0808856932345
5,0.0390870921"
df <- read_csv(txt)
# Convert NodeID column to factor first
df %<>%
mutate(NodeID = factor(NodeID))
# Plot
ggplot(df, aes(pageRank, fct_reorder(NodeID, pageRank))) +
geom_point() +
geom_segment(aes(y = NodeID, yend = NodeID, x = 0, xend = pageRank), color = "red") +
scale_x_continuous(expand = c(0, 0)) +
ylab("Node Rank") +
xlab("PageRank Value") +
theme_classic(base_size = 16)
ggplot(df, aes(y = pageRank, x = fct_reorder(NodeID, -pageRank))) +
geom_line(group = 1, color = "red") +
scale_y_continuous(expand = c(0, 0)) +
xlab("Node Rank") +
ylab("PageRank Value") +
theme_classic(base_size = 16)
Using base R plot
df$NodeID <- factor(df$NodeID, levels = c("1", "2", "4", "3", "5", "0"))
plot(df$pageRank ~ df$NodeID, xlab = "Node Rank", ylab = "PageRank Value")
Created on 2018-08-08 by the reprex package (v0.2.0.9000).