将空白插入向量中,例如R中的小刻度标记 [英] Insert blanks into a vector for, e.g., minor tick labels in R
问题描述
此问题通常与先前的评论,暗示将空白插入序列的功能可能会有用.
This question relates generally to a previous SO question concerning the creation of minor tick marks on a ggplot2
axis and specifically to a comment in the answer to that question suggesting a function to insert blanks into a sequence may prove useful.
由于我经常在类似的图上添加较小的刻度线,所以我在创建这样的函数时费了点力气(请参阅我的答案下方).
As I frequently add minor tick marks to similar plots, I took a stab at creating such a function (see my answer below).
推荐答案
以下功能允许用户请求向量的每个 n th 元素nth
x
可以用(1)替换为空字符占位符(empty = TRUE
;默认值),也可以用(2)从向量(empty = FALSE
)中省略.此外,它提供了请求反向操作(inverse = TRUE
;不是默认值)的选项.下面通过一些示例说明了该功能.
The following function allows the user to request that every nth element nth
of a vector x
either be (1) replaced with a empty character placeholder (empty = TRUE
; default) or (2) omitted from the vector (empty = FALSE
). Additionally, it provides the option of requesting the inverse (inverse = TRUE
; not default) of the operation. The functionality is illustrated with some examples below.
首先,函数:
every_nth <- function(x, nth, empty = TRUE, inverse = FALSE)
{
if (!inverse) {
if(empty) {
x[1:nth == 1] <- ""
x
} else {
x[1:nth != 1]
}
} else {
if(empty) {
x[1:nth != 1] <- ""
x
} else {
x[1:nth == 1]
}
}
}
一些替换或省略向量元素的示例:
Some examples of replacing or omitting vector elements:
numvec <- 0:20
charvec <- LETTERS
## Replace every 3rd element with an empty character
every_nth(numvec, 3) # conversion to character vector
[1] "" "1" "2" "" "4" "5" "" "7" "8" "" "10" "11" "" "13"
[15] "14" "" "16" "17" "" "19" "20"
every_nth(charvec, 3)
[1] "" "B" "C" "" "E" "F" "" "H" "I" "" "K" "L" "" "N" "O" "" "Q"
[18] "R" "" "T" "U" "" "W" "X" "" "Z"
## Omit (drop) every 3rd element
every_nth(numvec, 3, empty = FALSE) # vector mode is preserved
[1] 1 2 4 5 7 8 10 11 13 14 16 17 19 20
every_nth(charvec, 3, empty = FALSE)
[1] "B" "C" "E" "F" "H" "I" "K" "L" "N" "O" "Q" "R" "T" "U" "W" "X" "Z"
但是,为了创建较小的刻度线,最好使用inverse = TRUE
选项返回此操作的逆函数:
However, for the creation of minor ticks, it is preferred to return the inverse of this operation using the inverse = TRUE
option:
## Retain every 3rd element, replacing all others with an empty character
every_nth(numvec, 3, inverse = TRUE) # conversion to character vector
[1] "0" "" "" "3" "" "" "6" "" "" "9" "" "" "12" ""
[15] "" "15" "" "" "18" "" ""
every_nth(charvec, 3, inverse = TRUE)
[1] "A" "" "" "D" "" "" "G" "" "" "J" "" "" "M" "" "" "P" ""
[18] "" "S" "" "" "V" "" "" "Y" ""
## Retain every 3rd element, omitting (dropping) all other elements
every_nth(numvec, 3, empty = FALSE, inverse = TRUE) # vector mode is preserved
[1] 0 3 6 9 12 15 18
every_nth(charvec, 3, empty = FALSE, inverse = TRUE)
[1] "A" "D" "G" "J" "M" "P" "S" "V" "Y"
为了说明该功能在创建次要刻度线中的用途:
To illustrate the function's use in the creation of minor ticks:
library(ggplot2)
df <- data.frame(x = rnorm(1000), y = rnorm(1000))
## ggplot2 default axis labelling
p <- ggplot(df, aes(x, y)) + geom_point() + theme_bw()
p
## Add minor ticks to axes
custom_breaks <- seq(-3, 3, 0.25)
p +
scale_x_continuous(breaks = custom_breaks,
labels = every_nth(custom_breaks, 4, inverse = TRUE)) +
scale_y_continuous(breaks = custom_breaks,
labels = every_nth(custom_breaks, 2, inverse = TRUE))
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