问题
My input is
a<-c(1,2,3,4)
b<-c(1,2,4,8)
df<-data.frame(cbind(a,b))
My output should be
a<-c(1,2,3,4)
b<-c(1,2,4,8)
d<-c(1,4,12,32)
df<-data.frame(cbind(a,b,c))
can i simply say df$a * df$b please help. I am getting an issue with duplication. they are getting multiplied in matrix form and there is also issue with different length columns.
回答1:
In Base R:
df$c <- df$a * df$b
or df$c <- with(df, a * b)
In Dplyr:
df <- df %>% mutate(c = a * b)
回答2:
You must assign df$a * df$b to a new column in the dataframe.
df$c<-df$a*df$b
This adds a new column (df$c) which contains column a multiplied by column b.
来源：https://stackoverflow.com/questions/31824863/how-to-simply-multiply-two-columns-of-a-dataframe