Writing a function to calculate the average number of columns in a dataframe in R
I need to calculate the average of the columns in a dataframe by writing a function and then applying it. I realize this is easy to do with mean
and apply
, but I need to write my own function. I've made many attempts but don't seem to figure it out. Below are three of my attempts. I am new to R. I would really appreciate any suggestions.
mean_fun<-function(x){
mean_c[i]= sum(x[1:dim(x)],na.rm=TRUE)/length(x[1:dim(x)])
return(mean_c[i])
}
mean_fun<-function(x){
for( i in 1:ncol(x)){
s=sum(x[1:i],na.rm=TRUE)
l=dim(x[1:i])
mean_c=s/l
return (mean_c)
}
mean_fun<-function(x){
x=rbind(x,newrow)
for(i in 1:ncol(x)){
x[newbottomrownumber,i]=sum[i]/length[i]}
return(x[1303,])
}
Assuming all columns in your dataframe are numeric, here is the setup of your first function where x is a vector (column in mydataframe).
mean_fun<-function(x){
mean_c= sum(x,na.rm=TRUE)/length(!is.na(x))
return(mean_c)
}
apply(mydataframe,2,mean_fun)
Here's an example, slightly modifying your second try
mean_fun<-function(x){
mean_c = numeric(0)
for( i in 1:ncol(x)){
s = sum(x[,i], na.rm=TRUE)
l = length(x[,i][is.na(x[,i]) == FALSE])
mean_c[i] = s/l
}
return (mean_c)
}
USING
mean_fun(mtcars)
# [1] 20.090625 6.187500 230.721875 146.687500 3.596563 3.217250 17.848750 0.437500 0.406250
#[10] 3.687500 2.812500
Why not use it dplyr
?
You can get the average for all columns in your data file.
summarise_each(funs(mean))
If we apply it to mtcars
library(dplyr)
mtcars %>% summarise_each(funs(mean))
# mpg cyl disp hp drat wt qsec vs am gear carb
#1 20.09062 6.1875 230.7219 146.6875 3.596563 3.21725 17.84875 0.4375 0.40625 3.6875 2.8125