如何从大量数据中搜索和检索特定列

Question

我的数据看起来像这样

best..F1   
best..F2
.
.

基本上，我想提取名称以

开头的所有列

SELECT 
    i.observation_id,
    SUM(IF(i.value=5,1,0)) / counts.num as 'percent_positive'
FROM intervals i
inner join (
    select observation_id, count(1) as num from intervals group by observation_id
) counts on counts.observation_id = i.observation_id
group by i.observation_id
order by i.observation_id
;

有没有办法做到这一点，而无需逐个访问数据并找到它的位置？

Answer 1

您可以尝试grep，如下所示：

df[,grep("^best\\.\\.F",names(df))]

Answer 2

library(dplyr)
df %>% select(starts_with("best..F"))

Answer 3

我们可以使用startsWith

中的base R

df[startsWith(names(df), "best..F")]