Odtnhj

I asked two questions before about filling missing data:

(Ⅰ)Question_one
(Ⅱ)Question_two

It almost succeed when I follow the advice but still have one warning and one error.

I use codes below to import data from Excel. (You can download this file in this Google Drive website):

#read form clipborad, which is copied in "Example_a.xlsx"
# read dt_A
dt_A <- read.delim("clipboard",header=TRUE)
# read dt_B
dt_B <- read.delim("clipboard",header=TRUE)

Then, I change the charcter into "Date" format:

#Change "Date" to date format
as.POSIXct(dt_A$Date, format="%m/%d/%Y %H:%M")
as.POSIXct(dt_B$Date, format="%m/%d/%Y %H:%M")

However, when I use "complete" (adviced by AntoniosK) to fill the missing date, a warning occurs.

library(tidyverse)
# complete dates of data B using dates of data A
df <- dt_B %>% complete(Date = dt_A[1])

The warning is:

Warning message:
Column `Date` joining factors with different levels, coercing to character vector 

However, df seems to meet the expectation (Fig.1). Then, I ignore this warning and use codes adviced by Jay Achar:

library(dplyr)
library(lubridate)

df %>% 
 mutate(B_Value = ifelse(is.na(B_Value),
 lag(B_Value, 1) + (lead(B_Value, 1) - lag(B_Value, 1)) *
 as.numeric(difftime(Date, lag(Date, 1))) / 
 as.numeric((difftime(lead(Date, 1), Date) + difftime(Date, lag(Date, 1)))),
 B_Value)) %>% 
 mutate(B_Value = round(B_Value, 2))

There occurs an error:

Error in mutate_impl(.data, dots) : 
 Evaluation error: character string is not in a standard unambiguous format.

Could you teach me why there is a warning & an error?