使用 difftime 时出错 "longer object length is not a multiple of shorter object length"

Question

我使用以下代码计算连续两行的秒数差

set.seed(79)

library(outbreaks)
library(lubridate)

# Import data
disease_df <- measles_hagelloch_1861[, 3, drop = FALSE]

# Generate a random time for each day
disease_df$time <- sample(1:86400, nrow(disease_df), replace = TRUE)
disease_df$time <- hms::as.hms(disease_df$time)

# Combine date and time
disease_df$time1 <- with(disease_df, ymd(date_of_prodrome) + hms(time))

# Sort data
disease_df <- disease_df[order(disease_df$time1), ]

# Difference in days of two consecutive row
disease_df$diff <- as.numeric(difftime(disease_df$date_of_prodrome,
                                       dplyr::lag(disease_df$date_of_prodrome, 1), units = 'days'))

# Difference in seconds of two consecutive row
disease_df$diff1 <- as.numeric(difftime(disease_df$time1,
                                       dplyr::lag(disease_df$time1, 1), units = 'secs'))

这是结果数据框

和错误消息 longer object length is not a multiple of shorter object length。

您能否解释一下为什么 difftime 几天都可以正常工作，但几秒钟就会出错？非常感谢！

Answer 1

time1 列的类型为 "POSIXlt"。我不太确定为什么 difftime 和 units = 'secs' 不起作用，但如果将其转换为 POSIXct，它可以正常工作。

disease_df$time1 <- as.POSIXct(disease_df$time1)
disease_df$diff1 <- as.numeric(difftime(disease_df$time1,
                               dplyr::lag(disease_df$time1, 1), units = 'secs'))

Answer 2

显然 dplyr 对以下行不满意：dplyr::lag(disease_df$time1, 1) 因为 disease_df$time1.

的格式

将其转换为 POSIXct 是可行的，因此只需更新这部分代码：

# Combine date and time and convert to POSIXct
disease_df$time1 <- as.POSIXct(with(disease_df, ymd(date_of_prodrome) + hms(time)))

使用 difftime 时出错 "longer object length is not a multiple of shorter object length"

Error "longer object length is not a multiple of shorter object length" when using difftime

datetime

datediff

r