Question

我在基于if else条件限制数据集时遇到了问题。

这是我的数据框的一个例子：

mydf<-data.frame(chemical=c("Cd","Cd","Cd","Cd","Pb","Pb"),species=c("a","a","a","a","b","d"),scores=c(0,1,2,3,0,0))

我需要选择：对于每种化学品和物种，如果scores>0选择得分最小的行，否则选择0行

我可以做得最低分，但我似乎无法成功添加if else语句。

ddply(mydf,.(chemical,species),function(x) x[which.min(x$score),])

结束表应该是这样的：

chemical species scores
1       Cd       a      1
2       Pb       b      0
3       Pb       d      0

Answer 1

mydf %>% 
  group_by(chemical, species) %>% 
  summarize(scores = ifelse(any(scores > 0), min(scores[scores>0]), 0))

我不知道这是否更快，但只是为了好玩，你也可以这样做

mydf %>% 
  group_by(chemical, species) %>% 
  summarize(scores = min(max(scores, 0)))

Answer 2

这里有可行的解决方案，使用OP的原始逻辑，可能不是最优雅的代码

<强> plyr

ddply(mydf,.(chemical,species),
           function(x) x[if(any(x$scores != 0)) {which.min(replace(x$scores, x$scores == 0, NA))} else which(x$scores == 0),])

<强> dplyr

mydf %>%
     group_by(chemical, species) %>%
     do(.[if(any(.$scores != 0)) {which.min(replace(.$scores, .$scores == 0, NA))} else which(.$scores == 0),])

解压缩ifelse逻辑

# If none of the values are equal to 0
if(any(.$scores != 0))
# Find the index of the smallest values from a vector where 0 has been replaced by NA
{which.min(replace(.$scores, .$scores == 0, NA))} 
# Else find index of value equal to 0
else which(.$scores == 0)

Answer 3

这应该达到你想要的效果：

= TEXT(12345,"######000000") & "." & TEXT(12,"######000000") & "." & TEXT(0,"###000")

R根据if else语句选择行

3 个答案: