[英]Lapply instead of for loop in r
我想編寫一個函數,該函數返回一個2列的數據幀,其中包含每個州的醫院,該州的排名以num指定。
Rankall有兩個參數:結局名稱(結果)和醫院排名(數字)。 該函數讀取result-of-care-measures.csv文件,並返回一個2列數據框,其中包含處於每個州的醫院,該醫院的排名以num指定。
rankall <- function(outcome, num = "best") {
## Read outcome data
## Check that state and outcome are valid
## For each state, find the hospital of the given rank
## Return a data frame with the hospital names and the
## (abbreviated) state name
}
head(rankall("heart attack", 20), 10)
hospital state
AK <NA> AK
AL D W MCMILLAN MEMORIAL HOSPITAL AL
AR ARKANSAS METHODIST MEDICAL CENTER AR
4
AZ JOHN C LINCOLN DEER VALLEY HOSPITAL AZ
CA SHERMAN OAKS HOSPITAL CA
CO SKY RIDGE MEDICAL CENTER CO
CT MIDSTATE MEDICAL CENTER CT
DC <NA> DC
DE <NA> DE
FL SOUTH FLORIDA BAPTIST HOSPITAL FL
我的功能正常運行,但是最后一步(格式化2列數據幀)由以下循環完成:
new_data <- vector()
for(i in sort(unique(d$State))){
new_data <- rbind(new_data,cbind(d$Hospital.Name[which(d$State == i)][num],i))
}
new_data <- as.data.frame(new_data)
是正確的,但是我知道,可以通過lapply
函數對同一循環進行lapply
我的嘗試是錯誤的:
lapply(d,function(x) x <-rbind(x,d$Hospital.Name[which(d$State == i)][num]))
我該如何解決?
我假設您的d
數據已經排序:
new_data <- do.call(rbind,
lapply(unique(d$State),
function(state){
data.frame(State = state,
Hospital.Name = d$Hospital.Name[which(d$State==state)][num],
stringsAsFactors = FALSE)
}))
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