Get average in R with different number of variables

Question

I have an issue which i cannot solve! I have this data frame called GOLFRQuiz

  qname  uname first second third fourth fifth Best_try  Forums_Read_Count    
 quiz_1 Alex      85     28    28      0     0  85   390
 quiz_2 Alex      33     33    33     33     0  33   390
 quiz_3 Alex      25      0     0      0     0  25   390
 quiz_5 Alex      25      0     0      0     0  25   390
 quiz_1 marko     42     71    71     71     0  71    50
 quiz_2 marko     83    100   100    100   100  100   50
 quiz_8 marko     75      0     0      0     0  75    50

I am trying to get the mean for the Best_Try for the same uname and his/her forums_read_count and save them in a new data frame. The main issue, is that some users did 3 quizzes, others did 7 quizzes!!! so what i want is to be like this:

uname  best_try  Forums_read_count
Alex     42             390
marko    82             50`

For reproducing the data frame:

structure(list(qname = structure(c(1L, 2L, 3L, 4L, 1L, 2L, 5L
), .Label = c("quiz_1", "quiz_2", "quiz_3", "quiz_5", "quiz_8"
), class = "factor"), uname = structure(c(1L, 1L, 1L, 1L, 2L, 
2L, 2L), .Label = c("Alex", "marko"), class = "factor"), first = structure(c(6L, 
2L, 1L, 1L, 3L, 5L, 4L), .Label = c("25", "33", "42", "75", "83", 
"85"), class = "factor"), second = structure(c(3L, 4L, 1L, 1L, 
5L, 2L, 1L), .Label = c("0", "100", "28", "33", "71"), class = "factor"), 
third = structure(c(3L, 4L, 1L, 1L, 5L, 2L, 1L), .Label = c("0", 
"100", "28", "33", "71"), class = "factor"), fourth = structure(c(1L, 
3L, 1L, 1L, 4L, 2L, 1L), .Label = c("0", "100", "33", "71"
), class = "factor"), fifth = structure(c(1L, 1L, 1L, 1L, 
1L, 2L, 1L), .Label = c("0", "100"), class = "factor"), Best_try = structure(c(6L, 
3L, 2L, 2L, 4L, 1L, 5L), .Label = c("100", "25", "33", "71", 
"75", "85"), class = "factor"), Forums_Read_Count = structure(c(1L, 
1L, 1L, 1L, 2L, 2L, 2L), .Label = c("390", "50"), class = "factor")), .Names = c("qname", 
"uname", "first", "second", "third", "fourth", "fifth", "Best_try", 
"Forums_Read_Count"), row.names = c(NA, -7L), class = "data.frame")

Answer 1

I think you are looking for aggregate() such as:

df2 <- aggregate(df$Best_try, list(df$uname), mean)
colnames(df2) <- c("uname", "avg_best_try")
df2$Forums_Read_Count <- df$Forums_Read_Count[match(df2$uname, df$uname)]

Answer 2

You can try

library(dplyr)
df1 %>%
     group_by(uname) %>% 
     summarise(best_try=mean(Best_try), 
           Forums_read_count=unique(Forums_Read_Count))
#    uname best_try Forums_read_count
#1  Alex       42               390
#2 marko       82                50

Or

library(data.table)
setDT(df1)[,list(best_try=mean(Best_try),
      Forums_read_count=Forums_Read_Count[1L]) , uname]
#    uname best_try Forums_read_count
#1:  Alex       42               390
#2: marko       82                50