Dplyr - 使用其他动态命名的变量改变动态命名的变量 [英] Dplyr - Mutate dynamically named variables using other dynamically named variables
问题描述
我正在尝试使用动态创建的名称创建一个新列,并使用涉及其他动态创建的变量的表达式填充该字段.例如,考虑下面的数据框.
I am trying to create a new column with a dynamically created name and populate the field with an expression involving other dynamically created variables. For instance, consider the below data frame.
ID multiplier value1_2015 value2_2015 value1_2016 value2_2016
1 0.5 2 3 1 4
2 1.0 2 4 5 1
我想编写一个函数,该函数给定数据框和年份,然后仅计算相应年份变量的表达式,并将结果存储在名为 total_year
的列中,其中 year
是给函数的值.例如,如果表达式是
I want to write a function which is given the data frame, and a year and then evaluates an expression for only the corresponding year variables, and stores the result in a column called total_year
, where year
is the value given to the function. For instance, if the expression was
multiplier * value1_year + value2_year
我打电话给 my_fun(df, 2016)
我应该收到
multiplier * value1_year + value2_year
and I called my_fun(df, 2016)
I should receive
ID multiplier value1_2015 value2_2015 value1_2016 value2_2016 total_2016
1 0.5 2 3 1 4 4.5
2 1.0 2 4 4 5 9
这是我所拥有的
my_fun <- function(df, year) {
year <- enquo(year)
total_header <- paste("total", quo_name(year), sep = "_")
calc1_header <- paste("value1", quo_name(year), sep = "_")
calc2_header <- paste("value2", quo_name(year), sep = "_")
calc1_header <- enquo(calc1_header)
calc2_header <- enquo(calc2_header)
ret_table <- df %>%
mutate(!!total_header := multiplier * !!calc1_header + !!calc2_header)
return(ret_table)
}
当我尝试这个时,我得到以下 Error in mutate_impl(.data, dots) :计算错误:二元运算符的非数字参数.
When I try this I get the following Error in mutate_impl(.data, dots) :
Evaluation error: non-numeric argument to binary operator.
将表达式替换为类似 !!total_header := !!calc1_header
运行没有错误,产生正确的列名,但列中的值是字符串value1_2016",而不是来自名为 value1_2016
的列中的相应值.
Replacing the expression with something like just !!total_header := !!calc1_header
runs with no error, produces the correct column name, but the values in the column are the string "value1_2016", not the respective values from the column named value1_2016
.
推荐答案
在这里,我们不需要 enquo/quo_name
来表示 'year',因为我们正在传递一个数值.paste
的输出将是 character
类,使用 rlang
中的 sym
(如@joran 提到的)这可以是转换为符号并用 !!
求值.确保在 '!!calc1_header' 和 '!!calc2_header' 来评估特定对象
Here, we don't need the enquo/quo_name
for 'year' as we are passing a numeric value. The output of paste
will be character
class, using sym
from rlang
(as @joran mentioned) this can be converted to symbol and evaluated with !!
. Make sure to add braces around the '!! calc1_header' and '!! calc2_header' to evaluate the specific object
my_fun <- function(df, year) {
total_header <- paste("total", year, sep = "_")
calc1_header <- rlang::sym(paste("value1", year, sep = "_"))
calc2_header <- rlang::sym(paste("value2", year, sep = "_"))
df %>%
mutate(!!total_header := multiplier * (!!calc1_header) + (!!calc2_header))
}
my_fun(df1, 2016)
# ID multiplier value1_2015 value2_2015 value1_2016 value2_2016 total_2016
#1 1 0.5 2 3 1 4 4.5
#2 2 1.0 2 4 4 5 9.0
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