英文:
Selecting columns in R dataframe based on values of column in other dataframe
问题
I have translated the code-related portions for you:
我已为您翻译了代码相关部分：
# Dataframe 1
# 数据帧1
colname value
列名 值
col1 0.45
列1 0.45
col2 -0.2
列2 -0.2
col3 -0.4
列3 -0.4
col4 0.1
列4 0.1
# Dataframe 2
# 数据帧2
col1 col2 col3 col4
列1 列2 列3 列4
1 5 9 5
1 5 9 5
45 29 43 9
45 29 43 9
34 33 56 3
34 33 56 3
2 67 76 1
2 67 76 1
# Select relevant columns from dataframe 2
# 从数据帧2中选择相关列
features = sqldf('select colname from dataframe1 where value > 0.3 or value < -0.3')
# Build a string for selecting columns from dataframe 2
# 构建用于从数据帧2中选择列的字符串
stringValue = "col1, col3, col4"
sprintf("SELECT %s FROM dataframe2", stringValue)
Let me know if you need further assistance.
英文:
I have two dataframes as u can see below.
#Dataframe 1
colname value
col1 0.45
col2 -0.2
col3 -0.4
col4 0.1
#Dataframe 2
col1 col2 col3 col4
1 5 9 5
45 29 43 9
34 33 56 3
2 67 76 1
What I want to do is to firstly select all columns of dataframe 1 that have a value > 0.3 or value < -0.3. The second thing I want is to select all column from dataframe 2 that match this condition. So the columns col1 and col3 of dataframe2 should be selected into a new dataframe like below.
col1 col3
1 9
45 43
34 56
2 76
The solution I thought about is to firstly select the relevant columns as u can see in the code below.
library(sqldf)
features = sqldf('select colname from dataframe1 where value > 0.3 or value < -0.3')
After this to build a string in a for loop that should look like below. And paste this in a sqldf query to select to right columns from dataframe2. However I dont know how to build this string. U guys know this or have a other solution?
stringValue = "col1, col3, col4"
sprintf("SELECT %s FROM dataframe2", stringValue)
答案1
得分: 2
With your current dataframe1 only col1 and col3 will get selected.
library(sqldf)
features = sqldf('select colname from dataframe1 where value > 0.3 or value < -0.3')
sqldf(sprintf("SELECT %s FROM dataframe2", paste0(features$colname, collapse = ", ")))
col1 col3
1 1 9
2 45 43
3 34 56
4 2 76
data
#Dataframe 1
dataframe1 <- read.table(text = 'colname value
col1 0.45
col2 -0.2
col3 -0.4
col4 0.1', header = T, sep = "")
#Dataframe 2
dataframe2 <- read.table(text = 'col1 col2 col3 col4
1 5 9 5
45 29 43 9
34 33 56 3
2 67 76 1', header = T, sep = "")
<details>
<summary>英文:</summary>
With your current `dataframe1` only `col1` and `col3` will get selected.
library(sqldf)
features = sqldf('select colname from dataframe1 where value > 0.3 or value < -0.3')
sqldf(sprintf("SELECT %s FROM dataframe2", paste0(features$colname, collapse = ", ")))
# col1 col3
# 1 1 9
# 2 45 43
# 3 34 56
# 4 2 76
**data**
#Dataframe 1
dataframe1 <- read.table(text = 'colname value
col1 0.45
col2 -0.2
col3 -0.4
col4 0.1', header = T, sep = "")
#Dataframe 2
dataframe2 <- read.table(text = 'col1 col2 col3 col4
1 5 9 5
45 29 43 9
34 33 56 3
2 67 76 1', header = T, sep = "")
</details>
# 答案2
**得分**: 1
base R的一种处理方式：
```R
mask <- dataframe1$value > 0.3 | dataframe1$value < -0.3
dataframe2[, mask]
col1 col3
1 1 9
2 45 43
3 34 56
4 2 76
英文:
A base R way of doing this:
> mask <- dataframe1$value > 0.3 | dataframe1$value < -0.3
> dataframe2[, mask]
col1 col3
1 1 9
2 45 43
3 34 56
4 2 76
答案3
得分: 0
使用 dplyr（不确定是否相关），您可以执行以下操作：
df2 %>%
select(one_of(df1 %>%
filter(value > 0.3 | value < -0.3) %>%
pull(colname) %>%
as.character()))
这通过选择与 df1 中的字符串匹配的列名来工作，这些字符串在 filter 中起作用。
英文:
Using dplyr (not sure if it is relevant), you can do:
df2 %>%
select(one_of(df1 %>% filter(value > 0.3 | value < -0.3) %>% pull(colname) %>% as.character()))
This works by selecting column names that match one_of the strings from df1 that works within the filter.
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