在 R 中的循环中创建多个数据帧

Question

I am new to R and I don't know how to create multiple data frames in a loop. For example: I have a data frame "Data" with 20 rows and 4 columns:

Data <- data.frame(matrix(NA, nrow = 20, ncol = 4))
names(Data) <- c("A","B","C","D")

I want to choose the rows of Data which its values in column T are the closest values to the vector elements of X.

X = c(X1,X2,X3,X4,X5) 

Finally, I want to assign them to a separate data frames with their associated X name:

for(i in 1:length(X)){ 
data_X[i] <- data.frame(matrix(NA))  
data_X[i] <- subset(data2, 0 <= A-X[i] | A-X[i]< 0.000001 )
}

Thank you!

Answer 1

Since you didn't give us any numbers, it is difficult to say exactly what you need the for loop to look for. As such, you will need to sort that out yourself, but here is a basic example of what you could do. The important part that I think you are missing is that you need to use assign to send the created dataframes to your global environment or wherever you want them to go for that matter. Paste0 is a handy way to give them each their own name. Take note that some of the data frames will be empty. It may be worthwhile to use an if statement that skips assign ing the dataframe if (nrow(data3)==0) .

`Data <- data.frame(matrix(sample(1:10,80,replace = T), nrow = 20, ncol = 4))`
`names(Data) <- c("A","B","C","D")`
`X = c(1:10)` 


`for(i in 1:length(X)){ 
  data2 <- Data 
  data3 <- subset(data2, A == X[i])
  assign(paste0("SubsetData",i), data3, envir = .GlobalEnv)
}`