问题
Often times in research we have to do a summary table. I would like to create a table using tapply
in R. The only problem is I have 40 variables and I would like to basically perform the same operation for all 40 variables. Here is an example of the data
Age Wt Ht Type
79 134 66 C
67 199 64 C
39 135 78 T
92 149 61 C
33 138 75 T
68 139 71 C
95 198 62 T
65 132 65 T
56 138 81 C
71 193 78 T
Essentially I would like to get it to produce the means of all the variables given the Type. It should look as
C T
Age 72.4 60.6
Wt 151.8 159.2
Ht 68.6 71.6
I tried using
sapply(df, tapply(df, df$Type, mean))
but got an error.
Any guidance would be appreciated.
回答1:
Try:
> sapply(df[1:3], tapply, df$Type, mean)
Age Wt Ht
C 72.4 151.8 68.6
T 60.6 159.2 71.6
alternatively you can use colMeans
:
> sapply(split(df[1:3], df$Type), colMeans)
C T
Age 72.4 60.6
Wt 151.8 159.2
Ht 68.6 71.6
回答2:
You could use aggregate
:
res <- aggregate(DF[,names(DF) != 'Type'],list(DF$Type),mean)
> res
Group.1 Age Wt Ht
1 C 72.4 151.8 68.6
2 T 60.6 159.2 71.6
then transposing it :
m <- t(res[-1]) # convert the data.frame (excluding first col) in a matrix and traspose it
colnames(m) <- res[[1]] # set colnames of the matrix taking them from the data.frame 1st col
> m
C T
Age 72.4 60.6
Wt 151.8 159.2
Ht 68.6 71.6
来源:https://stackoverflow.com/questions/37730342/using-variations-of-apply-in-r