将日期范围内数据框某些列的值相乘，并基于 R 中另一列的值

Question

I am struggling with an ifelse statement in R. I have a data frame with 64 columns and 12861 rows. I need to multiply 10 of those columns within a date range (date is a column) and based on the value in another row (tdiff) and replace the old values with the new values in the data frame. This line of code results in a dataframe that is 12681 X 12681. It should be the original size of 12681 (rows) by 64 (columns). What am I doing wrong? Thank you in advance!

test<-data.frame(ifelse(slopejoin$tdiff==2 & slopejoin$date>="2021-01-30" & slopejoin$date<="2021-08-08",
     slopejoin[,c("a_Pinene","Isoprene","Methyl_Vinyl_Ketone","Nopinone","Benzene_", "D_Limonene",
                  "Sabinene","a_Cedrene","Pentane","Hexane")]*0.85,
     slopejoin[,c("a_Pinene","Isoprene","Methyl_Vinyl_Ketone", "Nopinone","Benzene_", "D_Limonene",
                  "Sabinene","a_Cedrene","Pentane","Hexane")]))

Answer 1

cols <- "a_Pinene","Isoprene","Methyl_Vinyl_Ketone", "Nopinone","Benzene_", "D_Limonene", "Sabinene","a_Cedrene","Pentane","Hexane")
x <- "2021-01-30"
y <- "2021-08-08"

# Replace values in original fields
slopejoin[slopejoin$tdiff == 2 & slopejoin$date >= x & slopejoin$date >= y,cols] <- slopejoin[slopejoin$tdiff == 2 & slopejoin$date >= x & slopejoin$date >= y,cols] * 0.85