在 R 代码中，我应该如何获得均值和标准差取决于“日”和“类别”列而不手动过滤

Question

I am getting Mean and standard deviation while filtering the below-mentioned columns in the R console, but how I should get the mean and SD without filtering the columns "Day" and "Category" without filtering it manually in the code and the result should print in the same CSV itself.

code should automatically create the depends on the column filter like below and print the results in the same CSV:

mean_Day1_Category_a, SD_Day1_Category_a,
mean_Day4_Category_b, SD_Day4_Category_b, etc...

data

Sex F_category        Value Day category
M   Food              25.6  1   a
M   Water             22    2   a
M   Food              22    11  a
M   Food             24.3   4   b
M   Food              24    5   b
F   Water            2.03   10  b

code

library(dplyr)
library(plyr)
library(doBy)
data <- read.csv("C:/Users/food.csv")
print(data)

data_male<- data %>% 
  filter(sex == "M")%>%
  filter(Day == 1)%>%
  filter(F_Category =="FC")%>%
  filter(Category =="a")

data_male

sd(data_male$value)
mean(data_male$value)

Answer 1

You have to group the data by day and category instead of filtering.

data_male %>% group_by(Day, Category) %>% summarise(avg_val = mean(Value), std_val = std(Value))