I have heart rate data in the form of a list with the four categories 1AS, 1CS, 1AI, 1CI each of variable size. I would like to output mean and standard deviations for each category in the list. I have the data in this format to calculate ANOVA and Tukey which I have done successfully but the mean has me stumped!
Group HR
1 1AS 300
2 1AS 280
3 1AS 260
4 1AS 250
5 1AS 300
6 1AS 272
7 1AS 250
8 1AS 198
9 1AS 200
10 1AS 195
11 1AS 214
12 1AS 249
13 1AS 240
14 1CS 250
15 1CS 236
16 1CS 200
17 1CS 272
18 1CS 206
19 1CS 203
20 1CS 237
21 1CS 214
22 1AI 218
23 1AI 276
24 1AI 240
25 1AI 264
26 1AI 300
27 1AI 315
28 1AI 300
29 1AI 285
30 1AI 286
31 1CI 167
32 1CI 233
33 1CI 214
34 1CI 219
35 1CI 214
36 1CI 246
37 1CI 230
38 1CI 218
Assuming your data is in a data.frame called DF:
by(DF$HR,DF$Group,mean)
# DF$Group: 1AI
# [1] 276
# -------------------------------------------------------------------------------------------------------------------------------------------------------------
# DF$Group: 1AS
# [1] 246.7692
# -------------------------------------------------------------------------------------------------------------------------------------------------------------
# DF$Group: 1CI
# [1] 217.625
# -------------------------------------------------------------------------------------------------------------------------------------------------------------
# DF$Group: 1CS
# [1] 227.25
by(DF$HR,DF$Group,sd)
# DF$Group: 1AI
# [1] 30.93946
# -------------------------------------------------------------------------------------------------------------------------------------------------------------
# DF$Group: 1AS
# [1] 36.48551
# -------------------------------------------------------------------------------------------------------------------------------------------------------------
# DF$Group: 1CI
# [1] 23.25595
# -------------------------------------------------------------------------------------------------------------------------------------------------------------
# DF$Group: 1CS
# [1] 25.77236
Another solution using ave:
ave(DF$HR, DF$Group)
gives the mean and
ave(DF$HR, DF$Group, FUN=sd)
with DF being your data frame.
来源：https://stackoverflow.com/questions/16776415/getting-mean-and-standard-deviation-from-groups-in-a-data-frame