英文:
subtracting two specifics row in multiple columns and the result as a new row
问题
以下是您要求的代码部分的翻译：
# 假设我有以下数据框：df <- data.frame("index" = c(1, 2, 3, 4, 5, "total"), "age" = c(10, 20, 30, 40, "non", 18), "1" = c(1, 4, 5, 6, 7, 9), "2" = c(8, 9, 5, 6, 11, 13))# 我想从第五行减去第六行的X1和X2列，然后将结果作为新行添加。我的预期输出应该是这样的：# （接下来是您提供的输出示例）# 我尝试了以下代码但遇到了错误：num_cols <- ncol(df)df_result <- data.frame()for (col in 1:num_cols) {if (col == 1 || col == 2) {df_result[, col] <- df[, col]} else {new_row <- df[5, ]new_row[col] <- df[5, col] - df[6, col]df_result <- rbind(df_result, new_row)}}
希望这有助于您理解代码部分的翻译。如果您需要进一步的帮助，请随时提出。
英文:
suppose I have following data frame:
df <- data.frame("index" = c(1,2,3,4,5,"total"),"age"=c (10,20,30,40,"non",18) ,"1"=c(1,4,5,6,7,9),"2"=c(8,9,5,6,11,13))
I want to subtract row 6 from row 5 in columnX1 and X2 and then add the result as a new row. my expected output whold be like this:
index age X1 X21 10 1 82 20 4 93 30 5 54 40 6 65 non 7 11total 18 9 130 0 2 2
I tried following codes but got erros:
num_cols <- ncol(df)df_result <- data.frame()for (col in 1:num_cols) {if (col == 1 || col == 2) {df_result[, col] <- df[, col]} else {rownew_row <- df[5, ]new_row[col] <- df[5, col] - df[6, col]df_result <- rbind(df_result, new_row)}}
答案1
得分: 2
你可以使用[来通过赋值创建新的行。df[x, 3:4]选择第x行和第3列到第4列。-是向量化的，所以不需要使用for循环。使用<-可以将新值赋给新的行。空列将被填充为NA。
df[7, 3:4] <- df[6, 3:4] - df[5, 3:4]# index age X1 X2# 1 1 10 1 8# 2 2 20 4 9# 3 3 30 5 5# 4 4 40 6 6# 5 5 non 7 11# 6 total 18 9 13# 7 <NA> <NA> 2 2
英文:
You can create a new row by assignment with [. df[x, 3:4] select the xth row and the 3rd and 4th column. - is vectorized, so not for a for loop. With <- you can assign the new values to a new row. Empty columns are filled with NAs.
df[7, 3:4] <- df[6, 3:4] - df[5, 3:4]# index age X1 X2# 1 1 10 1 8# 2 2 20 4 9# 3 3 30 5 5# 4 4 40 6 6# 5 5 non 7 11# 6 total 18 9 13# 7 <NA> <NA> 2 2
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