条形图在R ggvis中绘制x轴顺序

Question

我正在尝试将ggvis用于我的日常报告。我遇到的一个问题是，对于我打算在数据顺序中绘制x轴的数据集。但是，实际绘图以字母顺序显示。

是否有任何隐藏参数可以更改R中条形图的x轴顺序？

Step    LER
Pre 3.2
DS  2.8
SiARC   2.2
OPL 1.9
ILD 1.6
Oxide   1.5

library(ggvis)
ler <- read.csv("shinyapps/EUV/data/by_step_LER.csv")
ler %>% ggvis(x = ~Step, y = ~LER) %>% layer_bars()

Answer 1

library(ggvis)

ler <- structure(list(Step = structure(1:6, .Label = c("Pre", "DS", "SiARC", "OPL", "ILD", "Oxide"), class = "factor"), LER = c(3.2, 2.8, 2.2, 1.9, 1.6, 1.5)), .Names = c("Step", "LER"), row.names = c(NA, -6L), class = "data.frame")

ler$Step <- factor(ler$Step, levels = ler$Step)

ler %>% ggvis(x = ~Step, y = ~LER) %>% layer_bars()