How do I find standard deviation for gender specific sorted data set in R?

Question

So, I am using the data.frame 'studentdata' and I have sorted the males from the females. I also created a new column called HoursSlept. Now I must find the standard deviation for males in the column HoursSlept and the same for Females.

Can someone help me??

Here is what I did but I don't know what sd it is giving me.

Answer 1

If you want to do it your way you'd have to write:

sd(Males$HoursSlept, na.rm = T)
sd(Females$HoursSlept, na.rm = T)

Because Males and Females are data.frames and you have to pass one column from the data.frames to the function. A more elegant way would be not to split the data in two data.frames. Instead you could use dplyr's filter function.

library(dplyr)
studentdata %>%
    filter(Gender == "male") %>%
    summarise(sd = sd(HoursSlept, na.rm = T))

And the same for the females. Or as @MrGumble suggested both at once with group_by:

studentdata %>%
   group_by(Gender) %>%
   summarise(sd = sd(HoursSlept, na.rm = T))

Answer 2

library(Hmisc)
attach(studentdata)
summarize(HoursSlept,gender,sd)