R语言数据框条件舍入后格式异常及kable渲染问题求助

你遇到的问题核心是：数值型向量的格式统一性。循环处理后，数据框的数值列中同时存在整数和带一位小数的数值，但R的数值型列会统一显示格式（只要列内有一个带小数的数，整列都会默认显示小数位），导致kable渲染时沿用了这种统一格式，所有数值都显示一位小数，千位分隔符也无法正确作用于整数。

以下提供两种可行的解决思路，均能实现你的需求：

方案1：将数值转换为格式化后的字符串（直观可控） #

直接把数值处理成符合要求的字符串，让kable直接输出格式化好的内容：

library(knitr)
library(kableExtra)
library(dplyr)

f2<-data.frame(HEALTH=c("Heart","Head","Back","Hands","Eyes","Feet"),
               NO2   =c(2001.13, NA, 15.88, 0.832, 0.21111, 100),
               SO2   =c(NA, 300.1450, 1.550, 2.04, 3.99, NA),
               O3    =c(NA, NA, NA, NA, 2.115, 100.13))

# 自定义格式化函数，返回符合要求的字符串
custom_format <- function(x) {
  if (is.na(x)) {
    return("")  # 用空字符串替代NA，也可保留"NA"
  } else if (abs(x) < 10) {
    sprintf("%.1f", round(x, digits = 1))  # 小于10保留1位小数
  } else {
    format(round(x, digits = 0), big.mark = ",", trim = TRUE)  # 大于等于10取整+千位分隔符
  }
}

# 批量处理所有数值列
f2_formatted <- f2 %>%
  mutate(across(c(NO2, SO2, O3), custom_format))

# 生成表格
kable(f2_formatted, format = "html",
      booktabs = TRUE,
      escape = FALSE,
      col.names = c("Health effect", "cases/yr","cost/yr","treatment/yr"),
      align=c("l","r","r","r"),
      linesep="") %>%
  kable_styling(latex_options= c("HOLD_position"))

方案2：保留数值类型，在kable中自定义格式化 #

不修改原始数据类型，直接在表格渲染阶段指定每列的格式化规则：

library(knitr)
library(kableExtra)

f2<-data.frame(HEALTH=c("Heart","Head","Back","Hands","Eyes","Feet"),
               NO2   =c(2001.13, NA, 15.88, 0.832, 0.21111, 100),
               SO2   =c(NA, 300.1450, 1.550, 2.04, 3.99, NA),
               O3    =c(NA, NA, NA, NA, 2.115, 100.13))

# 先完成数值舍入（和你原逻辑一致）
custom_round <- function(a) {
  if(is.na(a)) {b <- NA}
  else if(abs(a) < 10) {
    b <- round(as.numeric(a), digits = 1)
  } else if(abs(a) >= 10) {
    b <-round(as.numeric(a), digits = 0)
  }
  return(b)
}

f2[, 2:4] <- apply(f2[, 2:4], 2, custom_round)

# 定义表格渲染用的格式化函数
format_num <- function(x) {
  ifelse(is.na(x), "", 
         ifelse(abs(x) < 10, sprintf("%.1f", x), format(x, big.mark = ",", trim = TRUE)))
}

# 生成表格并指定列格式化规则
kable(f2, format = "html",
      booktabs = TRUE,
      escape = FALSE,
      col.names = c("Health effect", "cases/yr","cost/yr","treatment/yr"),
      align=c("l","r","r","r"),
      linesep="") %>%
  column_spec(2:4, formatter = format_num) %>%
  kable_styling(latex_options= c("HOLD_position"))

内容的提问来源于stack exchange，提问作者Alex Young