Question

使用循环和条件语句，我想识别值大于2.50的行

customer <- c("john", "amy", "doug")
product  <- c("coffee", "pastry", "pastry")
store    <- c("a", "b", "c")
cost     <- c(5.50, 2.45, 3.00)

df <- data.frame(customer, product, store, cost)

我想识别超过2.50美元的购物并保存＆＃34;商店＆＃34;和＆＃34;产品＆＃34;作为与超过2.50美元的购买相关联的单独向量。

到目前为止，这是我的代码而且无法正常工作......

for (row in 1:nrow(df)) {
    customer <- df[row, "customer"]
    product  <- df[row, "product"]
    store <- df[row, "store"]
    cost <- df[row, "cost"]

    if(cost > 2.50) {
        print(paste(customer, "purchased", product, "at", store, "for", cost))
    } 
}

这不适用于工作，如何保存两个＆＃34;产品＆＃34;和＆＃34;存储＆＃34;作为单独的载体？

Answer 1

不需要明确的for循环。

这会分别保存store和product列cost > 2.5：

store.sel <- df[which(df$cost > 2.5), "store"]
product.sel <- df[which(df$cost > 2.5), "product"]

或dataframe

的子集

subset(df, cost > 2.5)

然后选择所需的列

with(subset(df, cost > 2.5), paste(customer, "purchased", product, "at", store, "for", cost))

Answer 2

您可以执行以下操作，输出您感兴趣的字符串的向量：

df2 <- df[df$cost > 2.5,]
with(df2, paste(customer, "purchased", product, "at", store, "for", cost))

## [1] "john purchased coffee at a for 5.5" "doug purchased pastry at c for 3"

Answer 3

我不确定你为什么要保存，但你可以这样做。

   df <- df[df$cost > 2.50,]
   cat(paste0(df$customer, " purchased ", df$product, 
       " at ",df$store, " for ", cost, "./n"))

循环和条件语句

3 个答案: