使用bsplus库链式调用中if语句引发逻辑参数解析错误求助

问题描述 #

原本可正常运行的bs_carousel代码如下：

library(bsplus)
library(reactable)

bs_carousel("info") %>% bs_set_data(interval = FALSE) %>% 
  bs_append(bs_carousel_image(image1, if(checker1 == 1){reactable(df1[,!(names(df1) %in% c("Day"))])})) %>% 
  bs_append(bs_carousel_image(image2, if(checker2 == 1){reactable(df2[,!(names(df2) %in% c("Day"))])})) %>% 
  bs_append(bs_carousel_image(image3, if(checker3 == 1){reactable(df3[,!(names(df3) %in% c("Day"))])})) 

为实现仅当对应数据框行数不为0时才执行bs_append，修改后的代码如下：

bs_carousel("info") %>% bs_set_data(interval = FALSE) %>% 
  if(dim(df1)[1] != 0){bs_append(bs_carousel_image(image1, if(checker1 == 1){reactable(df1[,!(names(df1) %in% c("Day"))])}))} %>% 
  if(dim(df2)[1] != 0){bs_append(bs_carousel_image(image2, if(checker2 == 1){reactable(df2[,!(names(df2) %in% c("Day"))])}))} %>% 
  if(dim(df3)[1] != 0){bs_append(bs_carousel_image(image3, if(checker3 == 1){reactable(df3[,!(names(df3) %in% c("Day"))])}))} 

此时触发错误：

Error in if (.) dim(df1)[1] != 0 else { : 
  argument is not interpretable as logical

但将整个bs_carousel代码放入相同条件判断中时可正常运行：

if(dim(df1)[1] != 0){
bs_carousel("info") %>% bs_set_data(interval = FALSE) %>% 
  bs_append(bs_carousel_image(image1, if(checker1 == 1){reactable(df1[,!(names(df1) %in% c("Day"))])})) %>% 
  bs_append(bs_carousel_image(image2, if(checker2 == 1){reactable(df2[,!(names(df2) %in% c("Day"))])})) %>% 
  bs_append(bs_carousel_image(image3, if(checker3 == 1){reactable(df3[,!(names(df3) %in% c("Day"))])}))}

错误原因 #

管道符%>%的作用是将左侧对象作为第一个参数传递给右侧的函数/表达式。当你在管道后直接使用if语句时，if会把左侧的carousel对象当作第一个参数（即.），但if的第一个参数要求是逻辑值，而非carousel对象，因此触发"无法解释为逻辑值"的错误。

而将整个carousel代码放在if内部时，if的条件是独立的逻辑判断（dim(df1)[1] !=0），管道在if内部正常执行，不会将carousel对象传给if的条件参数，因此运行正常。

解决方案 #

方案1：分步构建carousel #

先初始化carousel，再通过独立的if语句追加内容：

library(bsplus)
library(reactable)

# 初始化carousel
carousel <- bs_carousel("info") %>% bs_set_data(interval = FALSE)

# 条件追加df1对应的内容
if (nrow(df1) != 0) {
  carousel <- carousel %>% 
    bs_append(bs_carousel_image(image1, if(checker1 == 1) reactable(df1[, !names(df1) %in% "Day"])))
}

# 条件追加df2对应的内容
if (nrow(df2) != 0) {
  carousel <- carousel %>% 
    bs_append(bs_carousel_image(image2, if(checker2 == 1) reactable(df2[, !names(df2) %in% "Day"])))
}

# 条件追加df3对应的内容
if (nrow(df3) != 0) {
  carousel <- carousel %>% 
    bs_append(bs_carousel_image(image3, if(checker3 == 1) reactable(df3[, !names(df3) %in% "Day"])))
}

方案2：自定义条件追加函数 #

通过辅助函数实现管道内的条件追加，保持链式调用风格：

library(bsplus)
library(reactable)

# 定义条件追加函数
conditional_append <- function(carousel, condition, content) {
  if (condition) {
    carousel %>% bs_append(content)
  } else {
    # 不满足条件时返回原carousel
    carousel
  }
}

# 链式调用构建carousel
bs_carousel("info") %>% 
  bs_set_data(interval = FALSE) %>%
  conditional_append(
    condition = nrow(df1) != 0,
    content = bs_carousel_image(image1, if(checker1 == 1) reactable(df1[, !names(df1) %in% "Day"]))
  ) %>%
  conditional_append(
    condition = nrow(df2) != 0,
    content = bs_carousel_image(image2, if(checker2 == 1) reactable(df2[, !names(df2) %in% "Day"]))
  ) %>%
  conditional_append(
    condition = nrow(df3) != 0,
    content = bs_carousel_image(image3, if(checker3 == 1) reactable(df3[, !names(df3) %in% "Day"]))
  )

测试数据及相关代码 #

数据框定义 #

# df1
df1 <- structure(list(Date = structure(c(19305, 19306, 19311, 
19319), class = "Date"), Name = c("Green", 
"Blue18", "Yellow1", "Green14"
), Amount = c(NA_real_, NA_real_, 
NA_real_, NA_real_), Raised = c(NA_real_, 
NA_real_, NA_real_, NA_real_), Method = c("Not listed", 
"Not listed", "Search", "Not listed"), 
    Issue_Type = c("01", "01", "02", 
    "02"), Day = c(9, 10, 15, 23)), row.names = c(NA, 
-4L), class = c("tbl_df", "tbl", "data.frame"))

# df2
df2 <- structure(list(Date = structure(c(19327, 19332, 19333, 
19339), class = "Date"), Name = c("Red", 
"Blue18", "Blue18", "Green14"
), Amount = c(NA_real_, NA_real_, 
NA_real_, NA_real_), Raised = c(NA_real_, 
NA_real_, NA_real_, NA_real_), Method = c("Not listed", 
"Not listed", "See table below", "Not listed"), 
    Issue_Type = c("03", "02", "02", 
    "01"), Day = c(1, 6, 7, 13)), row.names = c(NA, 
-4L), class = c("tbl_df", "tbl", "data.frame"))

# df3（空数据框）
df3 <- structure(list(Date = structure(numeric(0), class = "Date"), 
    Name = character(0), Amount = numeric(0), 
    Cash_Raised = numeric(0), Method = character(0), 
    Issue_Type = character(0), Day = numeric(0)), row.names = integer(0), class = c("tbl_df", 
"tbl", "data.frame"))

# checker变量
checker1 <- 1
checker2 <- 1
checker3 <- 0

图片获取代码 #

library(png)
library(RCurl)
image3 <- readPNG(getURLContent("https://www.eas.org.uk/assets/images/logo-light.png"))
image2 <- image3
image1 <- image3

内容的提问来源于stack exchange，提问作者alec22