※ 引述《celestialgod (天)》之銘言： : ※ 引述《lovedmagic (EricZou)》之銘言： : : [問題類型]: : : 程式諮詢(我想用R 做某件事情，但是我不知道要怎麼用R 寫出來) : : [軟體熟悉度]: : : 新手(沒寫過程式，R 是我的第一次) : : [問題敘述]: : : 目前我遇到的困難是我有A1~A270個變數，我每個變數都有大概五個數值， : : 每個數值左側代表一個名稱，例如我A1這個變數裡面有 34 18 16 9 4五個值 : : 然後每個數值對應到左側的名稱有A B C D E ，我想做的就是取出A1變數中 : : 最大的那個值，然後再取出左側的ID，主要是要求出左側的ID，我要如何 : : 讓迴圈把每個變數都跑過一次呢??? : : 以下有錯誤範例 : : [程式範例]: : : fxck = data.frame() : : for (i in 1:270){ : : number[data$Ai==max(data$Ai)] : : fxck <- rbind(number[Ai==max(Ai)],Ai) : : print(fxck) : : } : : [關鍵字]: : : 多個變數、迴圈 : library(data.table) : DT <- data.table(name = LETTERS[1L:5L], matrix(rnorm(270L * 5L), 5L)) : setnames(DT, paste0("V", 1L:270L), paste0("A", 1L:270L)) : # direct: : data.table( : variable = paste0("A", 1L:270L), : ID = as.character(DT[ , lapply(.SD, function(x) name[which.max(x)]), : .SDcols = A1:A270]) : value = as.numeric(DT[ , lapply(.SD, max), .SDcols = A1:A270]) : ) : # variable ID value : # 1: A1 B 0.5974676 : # 2: A2 A 1.6205859 : # 3: A3 E 0.9247647 : # 4: A4 A 1.7180776 : # 5: A5 D 1.2060909 : # --- : # 266: A266 C 0.4813518 : # 267: A267 B 1.3096330 : # 268: A268 B 0.4504671 : # 269: A269 C 0.7401682 : # 270: A270 D 2.9256539 : # melt: : library(pipeR) : out <- melt.data.table(DT, 1) %>>% : `[`( , .(ID = name[which.max(value)], value = max(value)) , : by =.(variable)) : # variable ID value : # 1: A1 B 0.5974676 : # 2: A2 A 1.6205859 : # 3: A3 E 0.9247647 : # 4: A4 A 1.7180776 : # 5: A5 D 1.2060909 : # --- : # 266: A266 C 0.4813518 : # 267: A267 B 1.3096330 : # 268: A268 B 0.4504671 : # 269: A269 C 0.7401682 : # 270: A270 D 2.9256539 : # melt 2: : out <- melt.data.table(DT, 1) %>>% : `[`( , `:=`(maxRow = rank(value) == length(value)), by = .(variable)) %>>% : `[`(maxRow == TRUE) %>>% `[`( , maxRow := NULL) : # tidyr + dplyr : library(tidyr) : library(dplyr) : library(pipeR) : gather(DT, variable, value, -name) %>>% group_by(variable) %>>% : filter(rank(value) == length(value)) 可能是因為我表達得不夠清楚導致討論的方向不夠明確我在這裡說聲抱歉， 以下是我頭腦清醒後想出來的data的處理方式 X A1 A2 A3 1 member A 34 10 4 2 member B 18 90 64 3 member C 16 155 0 4 member D 9 202 1 5 member E 4 84 6 6 member F 0 50 4 7 member G 0 153 30 8 member H 0 0 30 9 member I 0 0 40 10 member J 0 0 14 11 member K 0 0 91 12 member L 0 0 0 13 member M 0 0 0 14 member N 0 0 0 15 member O 0 0 0 16 member P 0 0 0 17 member Q 0 0 0 18 member R 0 0 0 19 member S 0 0 0 20 member T 0 0 0 21 member U 0 0 0 22 member V 0 0 0 23 member W 0 0 0 24 member X 0 0 0 25 member Y 0 0 0 26 member Z 0 0 0 27 member AA 0 0 0 我主要是想求在我變數下最大的數對應到左邊的名稱 例如A1是member A 然後值是34接著A2是member D然後值是202 以下是我真正想要的解，個人寫的步驟有點詭異還會跑出warnings 但總歸是跑了理想的長相出來所以跟大家分享一下 A <- cbind() B <- cbind() for (i in 2:271){ colnames <- as.vector(X[data[,i] == max(data[,i])]) A[i-1] <- colnames B[i-1] <- max(data[,i]) } AB <- cbind(A,B) AB A B [1,] "member A" "34" [2,] "member D" "202" [3,] "member K" "91" [4,] "member J" "56" [5,] "member E" "298" [6,] "member B" "318" 以上謝謝之前各位大大們的回答 --

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